As for environments, they largely become irrelevant once you get bless, then you just bless everything and it heals instead. Drop some fire on your feet, bless it, bam time to heal with a Heal over Time Effect on me.
Now, there is no way we can tell if this will be the case at the release, but in recent video stream, bless seemed to require a source point so you no longer can bless like no tomorrow.
And Strength melee char have very low magic armor so they are the most vulnerable to terrain hazard. Still your mage can help them and all melee (rogues, warriors) do have a bunch of mobility spells, not to mention the polymorth fly.
I actually love the environmental effects I don't think there are too many, I think they really make the game what it is.