I would think druids would rock in battlegrounds, partially because of the randomness of battlegrounds and partially because of the plethora of tools they have at their disposal.

I agree, they lack focused burst, which takes away from their power in something like arena. If Nature's Swiftness applied to any druid spell (Starfire as well as Wrath), they would have similar burst to the Shammies Elemental Mastery combo.

They lack the fear protection, that stacked Tremors get.
They cannot self rez, once per toon, when everyone is dead.
They do not have grounding totems vs casters.
They don't have the passive healing from healing stream totems.

They do have similar levels of armor to the shammies, but need to drop the armor to heal.
Typhoon on round-robin, is similar to Thunderstorm.

They have two instant cast dots, which like warlocks do not require facing.
Both groups (druids or warlocks) are much more vulnerable to fear then shammies, but they can attack to a degree despite facing.
Also, Wrath is a much faster casting spell then Lightning Bolt, so Druids are much more mobile.
Rejuvenation and Lifebloom are heals which can be cast on the move.

Druids have Cyclone and Entangling Roots for crowd control effects.
Druids have stealth, which Shammies and Warlocks do not have.
They have AoE power between Hurricane and Starfall.
Between shifting from travel form to cat form, they are one of the best flag runners.

It depends on the game and battleground, and the opposition.
They won't do nearly as well in arena, but that is their lack of burst.
In any battleground with some level of cover, they can Starfire, Moonfire and Insect Swarm, which are all spells without travel time, so they cannot be found by tracking where the spells are coming from.

I think they'll do quite well in battlegrounds, as opposed to arena.
But play differently.