Even for 1 tree characters I think it's worth it to have 4 points in the two other tree's just for the +1 to all skills when you want it (first tier of jack of all trades).
Even only 4 points in the lightning spell is quite decent...giving a decent amount of damage from range, and a good chance to stun.
Mark of flame is more damage and hits multiple enemies as well, but if your not going pure sorc you might just want to go with lightning damage from your spell and 2 other elemental types on your weapons to cover all 3 bases.
Charged bow attacks always proc elemental effects.....so it's a great choice to use as a secondary weapon. Ice bows can be good for slowing down enemies.
Then your primary weapon can have fire damage for instance. That gives you fire, ice and lightning attacks.
There is no one element that is better then the others, but it is nice to have all 3 elements to call on quickly. If your only putting 4 points in sorc...that means you have lightning taken care of, and can the other two from weapons.
Does anyone know if adding multiples of the same elemental type will stack the amount of damage? If, for example, I add a hilt that does 15 fire damage with damage over time and I also add a gem that does 17 fire damage with damage over time, does that stack to 32 fire damage with the damage over time, or will it only take the higher stat (in this case, the gem) into effect and, more or less, negate the effects of the 15 fire damage hilt?
*Edit* OK, I tested this out and the effects will stack together, basically adding the base elemental damage together for an overall elemental damage and then the DOT is also added together for an overall DOT elemental damage.
I tend to favor Shocking damage as a mage, since the stun locks enemies in place for my AoE attacks. Freezing is good against big enemies, but you have spells for that too. Burning damage is probably the least useful. Sure it makes weaker enemies panic, allowing you to deal more damage, but it is a bit too situational. Shocking is far more reliable with the stun.
"I'd rather betray the world than let the world betray me." -Cao Cao