At level 14, fighting a casting mob, am I better off to use a hand drum
with Elemental Rhythms, or sing it while slashing away with a gnoll hide
lariat?

I tried both but wasn't high enough on the hate list to judge the
effectiveness myself and the tank didn't pay enough attention to whether
spells were hitting him or not.

The group was me, rogue-tank, shaman, two wizards, & a cleric. The casting
mobs were orc shamans in Oasis. I was twisting ER, CoB, and Bellow against
these guys. Non casting mobs I was twisting CoB, Bellow, & either another
Bellow or Hymn (rogues can't taunt, so we all ending up taking *some*
damage). It was only when the casting mobs got pulled that I tried using
instruments.

Peace
Evulia of Tunare