New recent gripe:
Recently noticed that splitting your offensive stats doesn't help you at all in the long run because somehow you end up doing less overall damage than focusing entirely on one or the other.
For instance, Thief/Rogue + Mage = Spellblade - so strength & willpower right?
Splitting between both made my spells do less damage altogether than focusing on Strength.
What?
As Savin states, a spellblade build basically requires you to go with Strength/Willpower/Cunning to do good damage.
Even then you'll run into problems when you want to fit all abilities you'd like to use. Or even some that fit thematically. Oh, and remember that you need a weapon that is both a good melee weapon and still a catalyst... which means you'll need either the spiraled blade or Elthara's Scythe (the latter is a bit better as long as you use two Lucky Strikes with it).
Good, speelblade themed abilties to consider are:
At-Will:
Blue Flame Blade, a stance that adds half your spellpower as magic damage to melee. You need to hand over your soul to Keros to get it though.
Psychic Blast, learnable from the trainer. Raw damage is nice and it's ranged. Doesn't benefit from Twist the Knife though.
Recharge:
Power Wave, which is stealable from Nakano and Kitsune Spellblade, a ranged storm spell that also counts as a melee attack and therefore benefits from Twist the Knife. The kicker? The CD is only
1 turn. This is the only recharge ability that counts as both a melee ability as well as a spell.
Acid Flask, stealable from Siorcanna Shaman. Deals damage based on Cunning and sunders armor for three turns, 2 turn CD. Perfect to keep up Twist the Knife, and increase melee damage due to sunder.
Cleave. Because AoE is nice to have, though you might have trouble with fitting it into this build. 2 turn CD.
Enchounter:
Deadly Shadow. AoE and gets you obscurement for three turns, keeping your threat low. You'll basically always want to start with this.
Smite Evil. Counts as both melee as well as a spell in the same way as Power Wave does. Does nice damage and restores resolve.
Ultimate:
Assassinate. Because it's either this or Kitsunetsuki, the latter of which requires you to use a one-handed weapon to use... which is a no-no at the moment since both the spiraled blade and scythe are two-handed.