I think you might just be. The Druid+Warrior/Warlock team is a good combination. I'm curious if spellsteal ends up being useful for the mage? It's a fairly costly spell and isn't necessarily going to drop the druid's mana. But if you can steal the HoTs and seal his casts (kick or CS), you may be able to kill the warrior. Also, using wound poison may help as the druid will probably want to remove it if he wants his heals to be more worthwhile. That may not sound too bad, but Abolish Poison ain't gunna do it quickly (you can probably reapply them faster, so no need to SS it).
If you can, try combining a successful stun with a shatter combo. He can't break it if he can't act

. Although you mentioned a high rate of stun resistance, so this won't be easy.
I'm no Arena expert as my rogue isn't geared well and only did it for a couple weeks, but that advice might work or be worthwhile trying. Personally, I think you might be able to kill the warrior if you can try to pull them apart. I'd say for you to stick on the warrior and try to kite him away (staying inside Intercept range and moving backwards... goat him into coming

) while your mage tries to push the druid around. No doubt the druid will go to help the warrior eventually, at this point, the mage will probably get cycloned and will need to break this or try to LoS it. The druid will either use Lifebloom or Rejuvination. I doubt he'll try a cast, but if he does, CS it. If he casts an insta-cast HoT, spell steal it. Keep trying to pull the warrior out of LoS and maybe your mage can help you.
This is all just bench fighting in my mind and good players may not fall for a separation

.