Just on Ice Block...it deals 104% of the Ice Blocked persons MAX health in damage to them over 4 seconds, so you gotta be quick...don't try to cast anything with significant cast time on them (i've found even a LHW is usually not quick enough, adding in human reaction time and possible GCD time on top of the spell cast time). I don't even think a HoT will tick soon enough. You need to hit them with something immediately that heals 4%+some of their health quickly. I hit them with Riptide (instant heal + hot effect) followed by a couple of LHW, which are now sped up because of talents that proc off of Riptide. You don't have to heal them much to save them from the Ice Block, but there are other dangers in the fight (as you know) and so they should be topped off anyway.