Freeze and dominate are game breakingly OP, flaming battle sphere is trash. The optimal talent path can change depending on what you find in terms of equipment or other talents, but here is what I think is best from base talents.
Ranger: Perfect Aim, Tunnel Shot, Perfect Aim 2. Storm shot next as soon as dex allows. (Perfect Aim 2 and Tunnel Shot can be swapped as preferred)
Rogue: Bear Trap, Sleep Bomb 2. Bear Trap 2 asap. Shadow Step.
Warrior: Power Strike, Shields Up 2, Shield Block, Recovery, Shield Block 2, Recovery 2. (Shield block and recovery order can be swapped depending on preference)
Duelist: Disengage 2, Lunge 1/2, Dash Attack.
Barbarian: Cyclone Strike. (Next: Charge 2, WM 1/2, whatever order you prefer)
Fire Mage: Mental Clarity 1/2, Burst of Flame, Flame Portal, Burst of Flame 2.
Storm Mage: Lightning Bolt 2, Mental Clarity 1/2, Shroud of Wind 1/2. Burst of wind is good for utility.
Ice Mage: Shield of Ice. After that, whatever you want, it's almost all great. You can play freezing cloud for the range, cone of cold 2 is crazy, and freeze is absolutely OP. I think freeze 2 is a waste, just get 14 int then stack dex for SP. Pick up a physical dmg weapon for crits on frozen enemies, gg.
Necromancer: Mental Clarity, Posion Cloud, Mental Clarity 2, Summon Skeleton, Posion Cloud 2. Pick up an alternate dmg spell/staff for enemy skeletons and poison yendor (I like Lightning Bolt, or if I have to shock). Aura of death is trash. Rush Summon Skelly Asap.
Enchanter: Discord 2. The rest depends on 2nd zone and if you get extra int. Get dominate ASAP. If I am feeling unsafe early I take Mirror Image (Amnesia it later). If not, just stack mental clarity and maybe take confuse for utility while waiting for the int.
It's important to hold talent points on mages for lvl 9 if you get no extra int, or lvl 6 if you get an extra int.