Just tried to run this about a half dozen ways with a decent group and after being wiped several times (literally “Rocks Fall; everyone dies”) we noticed the following issues:
1. Grast’s shield is unpredictable, we observed multiple instances of rocks falling through or it failing to activate at all. Also, one hilarious instance where it seemed to go out of sync (i.e. the shield would fall right as soon as the rocks started. )
2. Grast agros Colossus Rumblus immediately upon being revived at 50% health. This makes it very very difficult to keep him up considering the necessity of the shield.
3. As stated above, the intention seems to have been to interrupt the mob before it sets off the falling rocks, but the interrupt doesn’t seem to have an effect. Even when you knock the mob back or down.