In D2:ED the maximum level a couple people got to was 37, with 35 or 36 being more common. Taking advantage of a couple respawn locations, it is possible to get to level 40 or higher. IIRC one of the Larians mentioned the technical level cap was 60, but you'd need to use a trainer or something to reach it.
I boosted Whirlwind and Rush Attack a bit earlier in the game, but after reskilling when I got the battle tower, I only re-learned them to level 1. I tried Battle Rage once (and it did help), but I don't tend to use temporary boosts (potions or skills) unless I'm really having trouble with a particular battle, so didn't bother re-learning it.
I found low levels of Life Leech and Regenerate were good enough (especially with plentiful potions and level 1 of the healing spell), but if you've got the skill points to spare...
I maxed Mana Efficiency (level 5) since it cut the mana requirement to summon my creature, which meant I could summon it for a tough fight and still have enough mana left over to use the healing spell, or something.
Early in the game I used equipment with Wisdom bonuses, and later put points in myself, but I don't know if I'll bother with that when DKS comes out here.
