Pants, Depending on what you want to do when you want to do it is important for Sentinel.
Leveling: Watchmen / Juyo is probably your best choice since it gives you your burns that heal you and is pretty powerful. It may not burst down enemies but you are wanting to survive and get to the next group of enemies quicker so as to level quicker. Plus the Zen gives your heals to all players in your party so it can heal your companion.
This is currently my watchman build up to level 38
I have heard that you can switch to Combat / Ataru form at level 35 - 40 since by then you get the more powerful abilities in the tree.
The problem with Combat is the Ataru form doesn't hit till level 21 and then you have to spend a ton of points in the other related abilities to get it to shine for you.
I have heard people using the Focus tree more for PVP since it gives some healing and better ability to move and survive a bit.
For Guardian folk I have heard people that want to "tank" going more Hybrid with points in the defense and vigilance tree. Seems as though there are some skills in vigilance that help in the defense side of things and survivability. I made this real quick but notice I went hybrid for tanking purposes.
But you say Guardian Slash is the pimp skill in the tree. Well yes and no. If you look at it, the Overhead slash is the poor mans Guardian slash but can do more damage with the 6 seconds that are removed from the "Vigilance" skill in the Tier 4 Vigilance tree.
Plus it gives you the "Protector" skill in Tier 5 of the Vigilance tree. Basically you guardian leap to a "friend / companion" that is in trouble and this skill reduces the damage they take by 20%, but it also now reduces the damage you take by 20% due to this "Protector" skill. Then you jump back on target with Force Leap and you get "Unremitting" Tier 3 vigilance tree that reduces the damage you take by another 20%. I have read that these are additive not multiplied like in WoW.
Just my 10 cents on the Jedi Knight trees.