I saw a small damage increase with a 3400 dps Maximus vs. Burning Axe + Firebird off-hand. At the same time, I went from +119% fire damage to +99%. I rerolled 6% damage for a socket, so I lost some there, but if I can get a legendary socket token, then I'll reroll the socket to %dmg again.
Overall, it maybe was a loss, but I've been using Maximus with Disintegrate - Convergence (fire dmg) and Blizzard - Apocalypse (also fire dmg), Templar follower, Storm Armor - Power of the Storm, and Astral Presence passive. I can *almost* indefinitely channel Disintegrate. If I had some APoC on one of my items, I could spam more Blizzard. I also use Black Hole (Blazar or Spellsteal), Familiar - Sparkflint, and Energy Armor - Pinpoint Barrier. Other passives are Conflagrate, Elemental Exposure, and Unwavering Will.
Another old build variation is using Mirror Image - Duplicates and Slow Time - Point of No Return with the Illusionist Passive for lots of bubble stuns.
I run T3/T4 with my gear... still trying to get more Firebird pieces and other items, but it's fun being able to have a staff with low attack speed so I can use channeling spells and no AP generator.