In general threat has been OK for me, other tanks doing more but no issues with similarly geared DPS.
Considering multi mob pulls only here
1 - Can pull with it, but only on the first mob, by that time you should nearly be in range and start swiping until your thrash will hit all mobs, then Thrash, Swipe, Swipe until comfortable, then Mangle
2 - Only use Taunt if the mob is NOT looking at you. Yes it increases threat for a short period, but if someone does pull the boss off you, it will be on CD when you need it.
Just go in and do as much damage as possible. Can use mangle on one target but on a multi mob pull, Thrash > Swipe > Mangle for initial threat.
After you have them on you, can use Mangle again.
3 - Just run to the pack, Swiping / Thrashing until most are on you, maybe taunt the one that got away.
I prefer feral affinity for this reason - You can get to the mobs quicker. Balance would allow the use of thrash quicker - You want to use Thrash when it will hit as many mobs as possible.