As far as damage vs defense in Savage Worlds superheroes, I agree it takes a bit of work to balance. It's not as easy to plot how much defense you need versus how much damage is being dealt. Then you throw in the Heavy Armor rules, and it gets fun. I've played Supers in SW a lot more than I've run it.
We've got a guy in one of my groups that likes to over-analyze everything. He did a work up on exploding dice, and it was his contention that it did not add that much of an advantage. While his numbers are solid (they always are), it doesn't feel like they tell the whole story. It feels like it happens more often than his numbers say, and it certainly produces more of a reaction when it happens (as opposed to rolling more dice). It's just exciting. It makes the GM's job tougher, because of the tendency for characters to get lucky and one-shot your bad guys. I recall being concerned during a Deadlands game about throwing a Werewolf at them when they had a distinct lack of silver weapons, and then the Huckster blew it out of it's socks with a Bolt spell first round.
Also - a word on the term "exploding" that always makes me chuckle. The term from Savage Worlds is "Acing", but I've rarely heard anyone call it that. They always say "explode". The term explode is from 7th Sea. Although, in the Second Edition, they've unfortunately limited when dice can explode rather severely. But that's what everyone says.