One caster or a UMD spec can cast halt undead, even on elite, scrolls or spells, and there should be almost no problems except for wraith and wights.
If I am in a group and the caster does not have it, I think he is a gimp and will tell him/her so. SOrc or wiz, no excuse to not carry that spell asap. With all the undead you will be doing all the way to end game. (hint: even works in epic....)
My FvS went with UMD so I could use those scrolls.
Demand crowd control from the caster and tell 'em 'no haste' so they stay together and work together better.