I like the systems on Water Blast, Seismic Blast, Energy Melee, Staff Fighting, Gravity, Time/Temporal and Oil Slick Arrow.
Beam Rifle needs a tweak to make it easier to keep track of which targets have the Disintegration effect, but I think the bonuses are good.
I don't like the system on Radiation Melee. It's hard to see who is Contaminated, the extra damage is very small and it's stupid that your heal doesn't work if the target isn't Contaminated.
I don't really consider Eagle's Claw to be a combo and largely ignore whether or not I hit someone within the 3 second window.
I haven't played Savage, Psi Melee, Street Justice, Dual Blades or Titan Weapons.