The bomb tossing orcs in blood furnace are kind of unique. You are not going to find good places to LOS them. Also their attack is not a spell so silence will not help. There is an added level of difficulty as they will also drop land mines you need to move away from.

Your best bet is to burst them down, and not have your group huddled together to avoid the AOE splash damage. This was the first instance that I truly had trouble with my old priest and 4 mage group as these guys could 2 shot the entire group. On occasion you may be unlucky and end up with a group of 2 or even 3 of these guys together and it can be very hard to over come w/o a high level booster. I was not able to finish Blood Furnace till much later (Underbog and Slave Pens are much easier). The room with the beholder looking boss with the 4 waves of adds first was just too much for my group till mid to late 60's.

Overall in general, if your tank is a paladin, then avenger shield the casters on your pull and you wont have any problems. Deathknights deathgrip and druids/warriors charge etc.