I do 3 boomkins and had 3 on the PTRs do arenas; combined experience tells me you will get DESTROYED as a Boomkin vs anything with a healer or mage aoe. Treants have as much hp as a fucking Critter, takes an AEor two and bam they're gone; just cuz you have 15 instead of 3 or 9 doesn't change that fact lol

Issue 1: Melee. If you vs any melee, you will not be able to unshift to heal. If you do, they will DESTROY you. Stunlock if rogue(s). God forbid a 2h Warr MS'ing the fuck out of you. Unlike shamen, Boomkins have to give up 8-12k armor to use their heals, and boomkin hp is "naturally" low; at 70 with RAID gear you're lucky to break 9k; if you socketed sta for pvp gear you might have more hp but then you give up alot of power; Boomkins depend on those spell gems, we're a highly gear-dependant class, let alone spec.

Issue 2: Casters. Boomkin form is BAD vs casters; 5% crit is NOT worth the inability to heal. So you've lost a bonus right off the bat; and vs mages/spriests the only way you will even survive is to outlast their mana, ESPECIALLY spriests. Full-caster groups aren't uncommon, and in reality, you'd prefer them so you don't have to waste time/mana shapeshifting into Boomkin and out to heal; just stay unshifted since armor is meaningless and keep your HoTs up. DO NOT USE HT. It sucks, it's bad mana efficiency and too damn slow.

Issue 3: Combinations of the above: You get a resto shaman, resto druid, or holy pala healing that Warr and you are fucked, period. Everything outheals your dps since you can't use Starfire with the melee guy hitting on you and they'll all break roots(Hell even Roots' OWN DAMAGE breaks it half the time), cyclone is only good for stopping healers temporarily

Issue 4: Shamen have 3 trees of spells; one gets locked you've still got options. Druids have 2 trees. Tree one: Arcane(Which is ONLY Starfire & Moonfire. NOTHING ELSE.) Tree two: EVERY FUCKING SPELL YOU HAVE, be it Heals OR wrath/is/cyclone/tranq/hurricane/treants/barkskin, I am not fucking kidding when I say EVERY SPELL YOU HAVE EXCEPT MOON & STARFIRE IS SILENCED BY INTERRUPTS.

Bottom line is, unless you like to look stupid and give the rest of us druids a bad name by moonfire spamming, and you like having 2 dps spells and 2 dots, PERIOD, go with Shamen for arenas. Shamen have burst shocks, CL, insta-cast and don't have to unequip half their armor to heal. Druids are one trick ponies, spam moonfire and wrath or die. Maybe drop a Forest of Death, which is oneshotted by any AoE. Take your pick :P