The most important skills for a SK are:
1. Bold strike, The skill that does the most damage it's a must max.
2. Curse, it increases state damage and damages the enemy for every skill they use!
3. Fear, fears the target away.
4. Steal life, basically steals life and gives the stolen life back to you, it's maxed at 330lp / 2s, although it might damage more or less.
5. Violent slice, stuns the enemy and has a fair cooldown very nice!
6. Draconic overpowering, paralyzes the enemy, combined with fear it's very nice.
7. Hellzone grenade, it's a nice filler attack with good damage, downside is that the animation takes very long. (keep it at level 1 though)
For buffs you should max :
Draconic Protection.
Draconic Righteousness.
Draconic Spirit.
Intense Concentration.