"Placing top 5" doesn't mean anything; a month ago I ran a Gruul and first and second place made up 25% of the raid's damage output, so "Top 5" beyond those first two basically meant "I still suck hard, just not quite as much as those other guys." What's your DPS? Got any WWS parses?
Overall damage is very dependent on fight as well. Locks generally outdamage them, though, and on stand-still-and-nuke fights I think rogues and well-geared fury warriors do as well. Any movement (beyond moving with the boss) favors ranged because they don't have to move as much, and favors DoT classes even more. Fury warriors will own on any non-threat encounter (On Solarian, for example, our MT specced fury with good gear and placed ahead of most of the AoE'ers for overall damage O.o)
40/21 isn't something you spec into to replace 10/48/3, but the reverse. For a while (pre-2.2) 48/13 AB rotations were great, and in 2.2 48+ arcane AM spam was wtfawesome. In 2.3, 10/48/3 reigns supreme. In 2.3.2, not sure yet, haven't had a chance to read through the EJ stuff, but my gut feeling says that 10/48/3 will still outdamage x/4x/11 unless you never run into mana issues, since your mana efficiency basically dropped 10%.
As for gear combos, 164 hit above all else. Point for point, hit rating is around twice as good as +dmg and 3 times as good as crit until you're capped. Spell damage is still the best-scaling point-for-point beyond a reasonable amount of crit (you'll note that almost every BT mage has +12dmg in most sockets). Haste is also very good (better than +dmg or crit).
For gear upgrades, neck, back, and trinkets for sure. ZA and the new badges rewards hold some great stuff as well (the helm, sword, neck, and ring come to mind). Belt of Blasting is an expensive but incredible piece of gear if you can get it bought. I'd also change any green gems to stuff that gives crit or hit, at least, as well.
EDIT: This is my 1337 post :D
Edited, Nov 28th 2007 11:04pm by lsfreak