Bone Strike  

This spell does indeed start out as an AE spell but the longer the mob is up (may relate to the other mobs that pop) the number of targets it hits reduces.

The Goats DD is 10 seconds on the button with numbers hit at 6,12,10,5,7,7,7,5,1,1,1

so it seems that after 1m 30secs (on Ixt Ironhoof at least) it goes down to single target.

Tubs

This is inface an Area Effect spell, figured it out the hard way =/