Just finished my own watchman sentinel. Duoed all 4-man heroics with my DPS-specced sage friend and healer companions. The only bosses I had trouble with was the tyrant on Belsavis and the 4-man in the nightmare lands on Voss.
Sentinel is a cooldown-dependent class. If you don't remember to use rebuke when going up against silver mobs, you will get beat down to a sliver of health. If you don't supplement rebuke with saber ward and pacify on gold mobs, you will get your backside handed to you. Before you use a medpack, pop guarded by the force for 5 seconds invulnerability. Heroic moment doesn't just provide a minute of healing but also resets the cooldown on saber ward.
So let's review.
Offensive:
Leap -> overload saber -> zealous strike -> cauterize -> merciless slash -> slash, zen when you have 30 centering, repeat
Defensive:
Rebuke -> Saber Ward -> Rebuke -> Pacify -> Guarded by the Force -> medpack -> Rebuke
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As for random imps flagging you... don't use AoE skills (force sweep, cyclone slash) around them, as you enter PvP mode if it hits them. This will get fixed in 1.2 but until then you just have to be aware of the little republic flag on your character portrait.