my big tip is:
when fighting big sword or big spears who you can't vault-retreive, use your speed advantage to hit each of them a lash or a a kick (you can actually dish out damage more quickly when facing more than 2 opponents) then slow time, vault-retreive. Or alernateley, slow time, backflip to side to single one out, wait for his to strike then counter-retreive (parry-dagger)
blocking is ESSENTIAL in multi-enemy fights. but dont forget to backflip away from unblockables.
and USE THE WALLS to jump off and instantly knock down opponents. and use your power tanks, dont save them up unless you know that you will be facing so many guys you will have to use a haste (which drains all your power tanks) as in the elevator stage.