Sooo,
Recently I've been doing some legion, I didn't see a lot of legion stuff in guide, so I'd like to share little experience for those who intend to do legion on COR^^;, let me know if there are other legion suggestion too as I'm pretty new to it. Note that every pt do legion differently with different strat/setup, and I don't claim my pt/strat is the most optimal, so some stuff may be depending on how your ally do things.
1. Buffing:
Unlike VW where you have time to wait for ppl to clear gold chests or afk, time is very important in legion, sometimes 30 sec is the difference between kill 10 or 11 NM(Thus extra chance for drop), or time out with clear or no clear. Thus 45 sec PR recast+Snake eye 5/5 is must have IMO.
If you rolled a No.6 on chaos or something, just snake eye anyways for a chance for No.11. Even if it doesn't proc, it still enhances roll potency. If auto-11 proced, you can do 2nd roll right away. If not, random deal and reset PR recast time to do 2nd roll.
Don't bust, the time you bust and reroll isn't worth it. You need to wait for extra 45 sec to redo roll, and your DD isn't going to make that much difference in terms of killing speed between a bad number and good number.
Note that you have 4 min of free time in Lobby, so you can save random deal and maybeeeee bust once in Lobby, but after fight start, unless you're waiting for DD to unweak, don't spend too long on buffing, it's sometimes make or break with those buffing speed.
Another way is, if you're good, you can keep doing other rolls once you finished buffing and leave DD pt(usually the roll that benefits yourself, such as regain/snapshot/mattk), for extra chance to get a No.11 up, once you have a No.11 up, you can buff much faster in DD pt by doing DD buff->disband and bust it-->get into DD pt and do 2nd DD buff.
I know some pt takes 2 COR instead of 1 though, so alternative way is to invite 1st COR buff, invite 2nd, buff, invite 1st again until you have 4 rolls.
It's also possible that ally will need you to redo buff mid-battle to save time, but it's also quite dangerous to do so due to some pretty large TP move range. So it's probably a good idea to fill up roll macro with PDT- stuff.
ASA legs with PR recast- and PDT- fits perfectly for this, other slot are roll duration+ items. Obviously AF3+2 in body slot if you're doing regain roll for some reason.
2. DDing:
I usually /SAM in legion, each NM usually takes 30 sec~1.5 min to die, I found extra WS with Sek and meditate helps a lot due to such short duration of the fight. STR with hasso also helps fSTR2. I usually try to keep hunters roll up on some NM. Hunters + Pot-Au-Feu and some high racc swap such as Hajduk ring or racc body(I use Gunman's gambison, but mextli/T.abj body works well too)can easily cap racc on majority of legion mob, except Behemoth/harpy/Ixion. You can probably swap out some of the racc piece for higher dmg if you're in T1 hall and still able to cap racc. On Behemoth/harpy/ixion, if you have no Feint, you probably won't cap without BRD song. It's probably a good idea to prepare multiple TP set with different acc based on the mob and whether feint is available or not. If you use parser, check your parse data regarding racc and adjust TP set based on that particular mob so you're not over stacking acc nor way below the cap.
Note that Mul wave2 has enemy crit-hit rate- trait, so it may not be a good idea to TP in rancor in Mul 2nd wave(?)
I usually have BRD lock SV near entrance(and it's probably better to do so anyways), so usually there won't be BRD buff available, when you plan your DD strat, keep this in mind that not everyone can buff you.
Also, don't TP in bronze bullet....Sometimes Aftermath up can do 400+ dmg a shot, with triple shot proc it's good TP phrase dmg. Legion has much longer TP phrase compare with VW, so there are little room to gimp TP phrase dmg. If you TP in bronze you won't get much benefit from aftermath.
Regarding which WS to use in legion:
Personally I prefer WF most of the time. It's easier to buff(doesn't require BRD) with new staff, and you got aftermath after WS. Last stand pretty much need a BRD(which usually isn't available)and chaos roll to pop good numbers and no aftermath(sometimes aftermath from WF actually make up the dmg even if NM has higher MDB). However on some of the mobs you still have use last stand due to WF is totally ***on it. And depending on enemy evasion and whether feint is available or not, you may need to do some racc swap for last stand. Ideal last stand racc swaps are:
Body: Obviously Khepri is the best and has most racc and most dmg, but in case you can't get it, NQ or Gunman's Gambison is ok.
Back: Libeccio, you sacrifice 10 rattk for 10 racc.
Ring: Hajduk, you sacrifice 7 AGI for 16 racc, but just swap one of them.
Keep Thaumas, especially thaumas head/legs/feet. You lost way more dmg than other slot if you don't use thaumas. Maybe you can change Thaumas for Alruna, sacrifice 4 AGI 5 STR for 9 racc 9 rattk, but don't touch anything else.
Below are some of the info I found on specific mobs, this is assuming nobody is buffing you and you can only self buff(no firestorm, no attack/racc songs and so on) If you have a BRD singing attack songs, last stand may pop higher numbers than WF for majority of the NM though, so plan your strat based on pt setup.
Hall of An:
Behemoth:Last stand, this NM, especially 2nd wave, has pretty high evasion, you need racc swap+hunter's roll for LS to land properly without feint.
Turtle: WF, Assuming only COR and BLM are on it, if you /SAM you can Sek and SC darkness for BLMs to MB with Blizzaja. It's also weak against ice, so it may be a good idea to use ice shot for BLM nuke dmg boost?
Wyrm: I used WF, but I think properly buffed last stand can pop a bit higher number.
Harpy: I also used WF, easier to land since it has pretty high evasion.
Hall of Ki:
All wave 1 and 2 NMs(Hydra/Khim/Orthus) has shitty WF numbers, so just last stand everything. Water shot also did higher than fire shot if you're using damaging shots.
Mantis: WF is pretty good on Mantis. You can also dispel with dark shot.
Hall of Im:
Corse: WF
Vampyr: WF
Chair: Last stand
Naraka: WF. Another NM with PDT- that your WF will help a lot in terms of killing speed.
Hall of Muru:
Amph: Last stand, it seems to have high MDB.
Ixion: WF did pretty good dmg on it, and easier to land too since Ixion has HIGH evasion.
Sandworm: Depend on it's absorb dmg mode.
Ironclad: Last stand. Water shot also did higher than fire shot on this one.
Hall of Mul:
Wave 1 and 2 are same as T1 hall bosses.
Wave3 NM seems to have very high INT, WF got resist a lot more on both Gallu and Rex. I'm probably going to try last stand on Gallu next time.(My TP dmg wasn't bad on it, but WF dmg was shitty compare with other NM)
As for rex, it also resist WF a lot even though we have someone casting Impact. But unresisted WF did pretty good. So maybe next time when I do rex again I need to try different strat to fix all that resist.