Hello, I've been tracking ADF aircraft for a while now. They're active everyday at all hours.
DRGN/DRAGON is indeed a Multi Role Tanker Transport, and the 'Racetrack' patterns it often flys are likely air-to-air refuelling patterns. Where there are tankers on station, you could infer that there are fighters bombing up on fuel (outside of fast jets, the only other aircraft in the ADF fleet that I recall having an AAR capability are the C-17 and perhaps Wedgetail). You may sometimes see ADF contract/lease Learjets associated with these activities, perhaps indicative of some sort of ACM/GCI exercise, towed-target A2A gunnery practice, or perhaps playing some sort of EW role* (escort jammer, generating an adverse EW environment, etc).
Occasionally you may see Learjets heading out to sea and cutting some odd looking patterns off the coast. This may well be some sort of exercise, wether that be supporting an exercises involving RAN vessels or RAAF aircraft, towing targets for RAN AAW gunnery practice, or some sort of EW/ECM testing activity/exercise* versus RAN vessels.
*You can see some odd looking additional antennae and pods on some of the Learjets in the pics, and you may recall the 'serpent' that appeared on the WX RADAR off of Rottnest Island a while back (The Rottnest Monster as it was called in the news). It was associated with a RAN EX and an ADF contract Learjet's flight path. Perhaps someone screwed up programming the aircraft's ECM kit and it shot back some spoofed returns after being painted by the WX RADAR?
News story:
http://www.abc.net.au/news/2014-02-13/rottnest-monster-mystery-solved/5258964
I'm yet to see any combat aircraft or predominantly tactical aircraft; mainly transports and support aircraft. King Airs get a fair workout as NAV trainers (BFRT, HDSN), as VIP transport (EVY or ENVOY within Aus, ASY internationally), as Tac Transport or possibly surveillance judging by some flight paths and published capabilities (DNGO/DINGO). Hercs and Globemasters also get a run (set an alert for the serials A97- and A41-).
Of course, there's an active RAAF VIP fleet - Challenger 604's and 737 BBJ's (EVY/ENVOY within Aus, ASY/AUSY/AUSSIE outside, sometimes something rare like REGAL1 for the Queen). There used to be a fair few troop rotation flights out of DXB back to Aus on the Airbus leased from HiFly, but as Australia has drawn down in the MEAO there's much less of them (CS-TQY and others using ASY Callsigns when they're not doing other charters for HiFly). The MRTT fleet usually operates as DRGN/DRAGON, but you might see them up as WNSR/WINDSOR. The leased Learjets have a bazzillion alphanumeric Callsigns and usually seem to fly ferry flights, NAVEXs, or in support of exercises/testing activities.
The S76A SAR Helos sound interesting, as they are based at locations where aircraft with 'bang seats' operate. You could infer that if we're anything like other countries, they operate when aircraft like Super Hornet, Hawk LIF, and PC-9 are up; ready to help anyone who has to punch out, especially if they wind up in the drink. However, I'm yet to see evidence of their activity on ADS-B.
I have collected and collated this information from openly available unclassified information on the Internet. I setup serials as alerts (under the airline category) and use the alerts to identify Callsigns in use. From analysis of aircraft history within Planefinder, I was able to identify other Callsigns associated with ADF aircraft. By adding associated Callsigns as separate alerts, I have been able to identify additional ADF leased/contract aircraft.
I recommend having a look at the following websites for further information:
ADF Serials:
http://www.adf-gallery.com.au
SWLD ADF Callsigns:
http://www.swld.com.au/pages/aus_raaf_callsigns.htm
Please find at the end of this post a CSV list of Serials, Registrations, and Callsigns that I have collected from around the Internet and via the App. Copy and Paste into a Text Editor, save as .CSV, and open in an appropriate application; or Paste directly into your Spreadsheet app of choice and convert text-to-columns delimited by comma.
Setting Up Alerts:
Callsigns go under 'Airline' (e.g. ASY will alert for all ASYnnn series callsigns, but expect occasional variations on spelling of common callsigns due to new pilots, brain explosions, or fat fingers. Look at an aircraft's history to get an idea of common variations as well as to pickup other Callsigns in use)
Serials go under 'Tail' (Use partial or full, e.g. A36- for all RAAF BBJ, or A36-001 for just that aircraft)
If anyone has any concerns about the nature of this information and national security, I respectfully suggest they take it up with the ADF - they're the ones broadcasting it in the clear and likely already know the implications. Hence the fact you're unlikely to ever see tactical/combat aircraft broadcasting ADS-B.
As with any hobby, it helps to do your homework and read, read, read; but it's also nice when you can stand on the shoulders of others. Here's the scheme I (and many others) use for learning about such things: if you don't understand something - be it an abbreviation, a term of art, a concept - look it up via the Internet. Don't understand the explanation? Pull it apart down to keywords and look those up. Don't understand that? Well, I'm sure you get the picture. If you can't find anything, you're doing it wrong - learn how to use the advanced features of your preferred search engine, and learn more about search technique. It's bound to be SOMEWHERE out there, either implicitly or attainable via deductive reasoning and inference from available information (but the quality of your deductions is strongly correlated with the background knowledge you have built). I'm not usually a forums type person, but they're a good resource too: I've often found that most questions I have, have often been asked and answered before somewhere if I search for them. Above all, develop the ability to asses the quality and validity of information you encounter - this comes with time, but you can look up 'research skills' and begin building a skill base immediately.
(Not trying to be condescending or supercilious in the preceding para, genuinely trying to share what I know in order to help others)
I hope people find what I have shared enlightening, entertaining, and useful.
Enjoy

It's a great hobby, especially if you have an analytical bent. Cheers to Pinkfroot for the great App and ADS-B RXR network!
//LIST FOLLOWS//
Serial,Aircraft,Operator,Callsigns
A15-,CH-47 Chinook,Army,
A17-,Bell 206B Kiowa,Army,
A21-,F/A-18C Hornet,RAAF,
A22-,AS350B Squirrel,RAN,
A23-,Pilatus PC-9,RAAF,
A25-,S-70A Blackhawk,Army,
A26-,Falcon 900,RAAF,
A27-,BAE Hawk 127,RAAF,
A30-,Wedgetail AEW&C,RAAF,
A32-,Beech King Air 200/350,Army,"DNGO, DINGO, BFRT, HDSN"
A34-,C-27J Spartan,RAAF,
A35-,F-35 JSF,RAAF,
A36-,B737 BBJ,RAAF,"ASY, AUSY, AUSSIE, EVY, ENVOY, REGAL"
A37-,Bombardier Challenger 604,RAAF,
A38-,Tiger ARH,Army,
A39-,KC-30A MRTT,RAAF,"DRGN, DRAGON, WNSR, WINDSOR"
A40-,MRH-90,Army,
A41-,C-17A Globemaster,RAAF,
A43-,RQ-7B Shadow UAV,Army,
A44-,F/A-18F Super Hornet & EA-18G Growler,RAAF,
A45-,IAI Heron UAV,RAAF,
A9-,AP-3C Orion,RAAF,
A97-,C-130J Hercules,RAAF,
N24-,SH-70 Seahawk,RAN,
N48-,MH-60R Seahawk,RAN,
N49-,Bell 429 Global Ranger,RAN,
VH-EMI,Beech 1900,DSTO,
VH-ESM,Gates Learjet,ADF Contract,"FRCO, FNTL, FARM, CTRY, BOSN, BLDK, BNDR, FSC"
VH-FOX,Gates Learjet,ADF Contract,"FRCO, FNTL, FARM, CTRY, BOSN, BLDK, BNDR, FSC"
VH-HOF,Gates Learjet,ADF Contract,"FRCO, FNTL, FARM, CTRY, BOSN, BLDK, BNDR, FSC"
VH-HRP,Sikorsky S-76A Spirit SAR,RAAF,
VH-LAH,Sikorsky S-76A Spirit SAR,RAAF,
VH-LAI,Sikorsky S-76A Spirit SAR,RAAF,
VH-LCL,Dash 8 Hydro Survey,Surveillance Australia RAN Contract,
VH-LHN,Sikorsky S-76A Spirit SAR,RAAF,
VH-LHY,Sikorsky S-76A Spirit SAR,RAAF,
VH-LHZ,Sikorsky S-76A Spirit SAR,RAAF,
VH-RUA,Augusta A109E,Raytheon RAN Contract,
VH-SLD,Gates Learjet,ADF Contract,"FRCO, FNTL, FARM, CTRY, BOSN, BLDK, BNDR, FSC"
VH-SLE,Gates Learjet,ADF Contract,"FRCO, FNTL, FARM, CTRY, BOSN, BLDK, BNDR, FSC"
VH-SLJ,Gates Learjet,ADF Contract,"FRCO, FNTL, FARM, CTRY, BOSN, BLDK, BNDR, FSC"
VH-SND,Gates Learjet,ADF Contract,"FRCO, FNTL, FARM, CTRY, BOSN, BLDK, BNDR, FSC"
VH-YSA,Piper PA-34 Seneca,ADF BFTS,
VH-YSC,Piper PA-34 Seneca,ADF BFTS,
VH-SLF,Gates Learjet,ADF Contract,"FRCO, FNTL, FARM, CTRY, BOSN, BLDK, BNDR, FSC"
VH-KNU,IAI 1124 Westwind,ADF Contract,"FRCO, FNTL, FARM, CTRY, BOSN, BLDK, FANL"
VH-KNS,IAI 1124 Westwind,ADF Contract,"FRCO, FNTL, FARM, CTRY, BOSN, BLDK, FANL"
//LIST ENDS//