My primary character also uses the Mage/Warrior/Druid combo. So here's some of my insights:
I leveled as Mage/Warrior and picked Druid only after the other two classes had already been maxed (or nearly so). So I can't really speak about any kind of build order for leveling these days, and I'm so overpowered that I can one shot most things outside instances. That said...
I've never really gotten much mileage out of Mage/Warrior. M/W elite skills are mostly buffs and passive skills. The buffs are useful while leveling but are of questionable usefulness late game. The elite skill at 50 gives you a passive casting speed boost which procs when you cast Flame or Fireball. While it only lasts a short time and has a cool down period before it'll proc again, when it's up, it is just short of awesome when stacked with other casting speed bonuses (Elemental Catalyst skill and Unbridled Enthusiasm potion) can get your Flame cast time below 1 second.
And Mage/Druid IMO blows all that out of the water for two reasons:
1) You can heal yourself and others. This is pretty self explanatory.
2) You get Magma Blade which if you work into your casting cycle would make up for the lack of the casting speed buff.
2a) In Siege, Magma Blade is a god send simply because 95% of the time, you don't have time to cast Flame.... or Plasma Arrow... or even Electric Bolt at times.
2b) In instances, the casting cycle I use is Flame>Magma Blade>Flame>Fireball>Repeat. Lightning is only leveled high enough to max out its root ability and is used ONLY to root stuff (although the extra damage is nice).
I imagine this wouldn't be too different while leveling. Flame>Lightning>enter 2b Cycle. If your Lightning's cooldown ends and the target isn't dead yet, you're taking too long to kill it and probably died by then.
well, there are a few things that didnt really make sense in there >_> but oh well lol.
for m/w i found it to be more useful for just about anything mainly because of how FAST i can kill things, no need for heals (and when there are, i have ph potions XD) however, il list all the consumables you can you to boost your speed/damage.
DAMAGE: Useful for instances/mobs with low Mdef or where you already have plenty of Matt.
Crispy Chicken Drumstick (Bought from ancient memento venders throughout the game.)
Lettuce Sandwich (made Via the Cooking skill or bought on the Auction house, Does NOT stack with Crispy Chicken Drumstick)
Magic Tambourine (made Via the Tailoring skill after doing the quest given by Dimitar Windwhisperer in logar for magical instruments or bought on the Auction house as a Magical Instrument Package with a random chance to get any instrument.)
Moti Blended Sausages (made Via the Cooking skill or bought on the Auction house, Stacks with everything)
MAGIC ATTACK: used for instances which High Mdef or where you're just lacking on Matt.
Loaf of Magic Hard Bread (made Via the Cooking skill or bought on the Auction house)
Loaf of Handmade Black Bread [EXPENSIVE] (made Via the Cooking skill or bought on the Auction house, Does NOT stack with Loaf of Magic Hard Bread)
CASTING SPEED: note that Demonic Ruins Potion is
NOT a casting speed pot but a critical hit potion that i use INSTEAD of the Arcane potion when my Flame cast time is already at at 0.5s without it.
Ancient Spirit Water/
Witch Doctor Elixir (made Via the Alchemy skill or bought on the Auction house)
Arcane Potion/
Demonic Ruins Potion (Bought from ancient memento venders throughout the game.)
Clear Thought (Possible reward from your Housemaid at Level 31+ Crafting and does NOT stack with Ancient Spirit Water/
Witch Doctor Elixir)
Magic guitar
(made Via the Carpentry skill after doing the quest given by Dimitar Windwhisperer in Logar for magical instruments or bought on the Auction house as a Magical Instrument Package with a random chance to get any instrument.)
I'm most likely missing something here lol so if you have any questions, feel free to pst me in-game on Artemis or make another post!