Warrior casts charge. Warrior casts intimidating shout. Druids trinket. Priest casts psychic scream. Druids lose .. This is obviously simplified, but you get the picture. For ganking the druids would be pretty fun but on pvp realms you get known real quick. Besides being outnumbered on my realm, most of the people I've killed once randomly at large in the world rarely square up to see if there are followers with me or stick around going "wtf, theres 4 with the same name..." NO they just iceblock/shield/reflect or w/e and run away. For arena I think 5 boomkin would be weak seeing as most teams will set up behind poles so even if you get the first kill off, after that you'll be chain CC'd FTL. 4 Boomkin + 1 resto shaman might be strong since you'd be poly immune, high armor, and fear immune.

Now, if you could make a QUICK and effective system of macros for cycloning multiple enemies with minimal numbers of keystrokes you'd be on to something. Simultaneously cycloning 4 targets while you nuke the straggler would be OP as hell. To be honest, 4 boomkin sounds like alot of fun and I might give it a whirl depending on how my shaman DPS fairs at 80. It looks like lava burst should be good, but alot of beta testers are still QQing about scaling issues (being 50% behind Warlocks and mages, 30% behind boomkins in raid dps) so we'll see. Do you have a boomkin team? I'd be interested to see how you do