The Sentinel Advanced Class is a Pure DPS Melee class with varying degrees of Operations utility depending on the spec. The Watchmen tree brings extra interrupts and a raid wide 6% heal about every 30 seconds if managed well and the Combat tree provides more spontaneous burst and increased Ops wide movement speed from the Transcendence Predation buff.
Unique Sentinel Mechanic:
What separates Sentinels from Shadows and Guardians (aside from the fact that Sentinels can't tank) is Centering
which is built up by using abilities that spend Focus. At 30 stacks of Centering the abilities Zen
become available and are your main raid utility abilities. Zen should be used nearly all the time because of how it affects each spec. Inspiration should be used at your raid leader's discretion, however it it most often used at the beginning of the fight (or shortly thereafter) for the possibility of being used later in the fight. Transcendence is mostly a Defensive/ Mobility skill that shines in PvP but has several uses during boss fights were mobility is key.
Defensive Cooldowns/ Abilities:
Additional Rating Information
A few gearing and modification tips.
Armorings/ Hilts: Always go for the Strength heavy armorings and hilts. Always.
Mods: When looking to increase your overall damage the mods you should use are the Deft Mods
(just plain 25, 26 and 27) and the Potent mods
Enhancements: Each enhancement should be the 27 End/ 41 Rating A/ 57 Rating B and their counterparts depending on which of the Secondary stats you're working on.
Basically what I'm getting at here is that if your mods have more Endurance than Strength or Secondary Stats you're wrong and should feel bad.
In the Event that Torhead's talent calc is bugged, here are the links to the builds I've posted from another calc.
31/7/0 + 3
5/31/2 + 3