This may or may not be anecdotal, but uh, Decoy shot. lol.
So much yes. Had a group the other night that was PLD WHM GEO RNG RNG COR. First couple runs were a little iffy on PLD keeping hate. Mentioned Decoy a couple times and the PLD started actually tanking with his back to us, and hate problems were a non-issue after that. No huge knockback problems in this fight, so it's very much viable (since frequent knockback is one thing that does sometimes warrant a tank staying back-to-wall over positioning to allow for Decoy). Our PLD still gathered everything up in the starting corner, but then he just moved out a bit and faced the group of mobs that were between the PLD and the wall/corner.
Since we had two RNG, we staggered Decoys a bit so the PLD nearly always had one of us piling more hate onto him. However, even if you have only one RNG that should still be a big help - use Decoy near the start of the fight if that's the case.
Every once in a while, imps would still occasionally wander away from the tank with some of the massive Last Stands we were firing, but I found that with two or more good DPS going to town, the imp never lives very long anyway after looking away from the PLD. Another big WS and they're pretty much dead, so it was not a real big problem for us.
Annihilator can be nice, but certainly isn't a requirement. I was fulltiming Armageddon (cuz it's my only ranged RMEA) and using Last Stand only, aside from Wildfire to trigger AM3. Worked great, Decoy with those ~15k+ AM3 proc ranged crits (sometimes twice an attack round with Double Shot up) really help the tank out a ton. Occasionally I'd over-TP a bit just because Empy "white damage" is strong enough that I was still doing great DPS while continuing to load the tank up with hate.
In the dozen I did day one, less than half the rangers/cors had a snapshot set at all. all but one did less damage than me, and I last stand in 5/5 meg+2. with a homestead gun. and hepaspara as my main hand lul.
I get your point, but to be fair, 5/5 Meg+2 isn't bad at all for COR Last Stand. Hands are BiS gear, and the other 4 pieces are like the next best alternatives to Relic +2/+3 (head/feet), AF+3 (body), and really well augmented Herculean Trousers. Of course, the relative ease of putting together a very good COR Last Stand set (and frankly, Meghanada/Mummu gear is pretty decent even for ranged TP) does make it all the more infuriating to see so many CORs who can't manage to put out respectable ranged damage...
In addition to so many ranged players not bothering to put together a preshot set, I also see a lot of people ignoring Flurry on the ranged DPS unless you badger them for it. Surely someone can come /RDM and know how to cast Flurry. Also worth noting for Ambuscade that if anybody has a RDM mule, a pre-entry Flurry II with Composure may well last long enough to cover your ranged people for the entire fight, or at least the majority, as long as you have decent enhancing duration gear (not hard: 5/5 Empyrean set and JSE cape is already a great start, even without Ammurapi/AF+3 hands/Relic+3 body). Particularly for this month's Vol.1 fight, you still wanna bring someone in who has RDM or /RDM though, in case Flurry gets dispelled.