With a lot of people here. The Rock worm does a great job if it's set and ready and you move vehicles in to attack. In that situation - sure OP. But then there's pretty much every other situation where their slow movement and need to burrow down before moving cost you dearly.
The situation above with a widow maker and a Rockworm holding a spot is as good as it gets and just screwing with the Rockworm using air or troops is super easy, even then.
The other one is a stealth harvester attack - it can pop up between 2 harvesters and take them both out before the other guy can respond.
Generally - relying on those slow mo fo's to take command points is a huge waste - I've lost plenty of matched waiting for them to finally pop up and waste a few wolverines.
I'm still low level (29) but I plan to drop the Rockworm for a leveled up giga cannon in the next day or so.