Mage power is one that really helps the Sk out, normally, 75 matk or whatever the matk bonus is for the particular weapon is not useful for mages. For tanks without matk masteries, 75 matk may increase by a third or a fourth their matk, greatly increasing the chance of landing debufs and damage dealt with magic. The main weakness of the SK is their low Last Chaos Gold and HP, they stun almost as easily as mages, and unlike all other tanks, the SK has no self-mdef buf.
In PvE, and PvP the SK has many options available to them. With the highest strength of all tanks and an affinity for damage, the SK can solo efficiently. While it is true that a Dark Avenger with a panther, or a Paladin fighting undead mobs can kill fairly quickly, both are limited. The SK at highest levels has four ranged nukes.
The first is the The Dark Elf racial drain nuke, which returns 20% hp of the damage done. Second is the Dark Elf racial ice bolt nuke which has a chance of slowing, effect 2 effectively a force slow attack. Third, they have the SK-only special nuke, which has half-power of the racial dain but returns 100% damage done as hp, and is fairly mana efficient. Fourth, and perhaps most feared, is the SKs lightning strike, which does damage and has a chance to land a 2 minute paralyze.