As people have been saying it's pretty great with a forge gun as it won't have the armor weighing it down making it even slower and the shields regenerate very quickly. In CQC with a hmg, it's all about the incredibly fast regen in comparison to other heavies. If you can get a breather you can wear down the enemy and if you have back up that is forcing them to stay back, you should be able to hold on. For Caldari and likewise minmitar, it's all about knowing when to engage and when to disengage. Brick tanks are slow, so you use that to your advantage. Also as a side note, don't use the assault. I thought its higher optimal would be useful but with having used it for a while the higher optimal is pointless since it does about a 3rd less damage than the standard and that higher optimal is often pointless since the gun will fire wildly at long range, I think it doesn't overheat as fast either but this is moot as the other heavy that will kill you with a standard hmg won't overheat either.

Also as long as you don't stack too many shield extenders your recharge delay is near instant, (I think it's one second.) So if you stack damage mods and rechargers on your Caldari sentinel you are probably better off than if you had put on extenders. I'm often greatful when I get fluxed from around a corner because it makes my regen immediately kick in instead of when my shields were at say 100 waiting for the longer tick.

The biggest let down on the Caldari sentinel for hotfix charlie was the slot layout modification. The Standard sentinel is basically useless as it doesn't have a low slot. With no low slot you have no way to passively rep your armor so you will be worn down. Some may say that you could get a logi, but the entire appeal of the Caldari sentinel over the other sentinels is the fact that it is the most independant. Able to regen at insane rates in comparison to the others allowing it to tank without a logi.