Sneak Attacks with spells follow the normal rules for sneak attacks
Specifically, the phrasing of sneak attack only specifies weapons in the section on nonlethal damage (which cannot normally be dealt with spells anyways). Touch attacks, ranged touch attacks and other such attacks caused as part of spells may therefore be used to deliver sneak attacks so long as they fulfill the normal conditions of a sneak attack.
In other words, sneak attacks with spells must meet the following conditions:
- The spell requires an attack roll (otherwise, it is not an "attack" for the purposes of sneak attack)
- You are flanking the target or it is denied its Dexterity bonus to AC.
- Ranged attacks are made within 30 feet
- The spell must deal damage
The 3.5 rule limiting volley attacks (such as scorching ray) to 1 sneak attack unless they are made using a full-round action is technically not a part of Pathfinder, though it is a perfectly reasonable ruling on the DM's part.
An Arcane Trickster's Surprise Spells ability is an exception to the above rules—one could, for example, cast a fireball in the surprise round and sneak attack a large number of opponents.
Damage Type: Sneak attack damage is of the same type as the original damage, with the added subtype of precision.
Is there no way a creature can stop the Sneak attack?
If it's able to impose disadvantage on the rogue's attack, then the rogue will not be able to do a sneak attack, even with support. However, imposing disadvantage on somebody is not that easy and most enemies may not have this ability.
Especially in early levels, rogues outdamage warriors, if there is a single target that is attacked by two characters. The rogue will get the sneak attack and that is indeed powerful.
However, that assumes that you have two people to attack a single enemy. Speaking in football terms, when you have your two front line people fighting the same enemy and you have as many enemies as characters, now there is one free to do as he pleases. Blitz the Quarterback, or rather the mage for example. So assuming your mage does not want to get into melee, you now have two enemies free (the one that the mage did not engage and the one that your warrior/rogue combo did not engage when they doubled on one enemy).
So while your rogue is making his powerful sneak attack, a number of things may happen:
- two enemies may attack the mage, that is not happy to have even one of them
- three enemies might pile on either the rogue or the warrior (or any other party member that is holding an enemy at bay, for example the cleric)
- two enemies are free to use range weapons
- two enemies are free to cast uninterrupted
- two enemies are free to get help
- two enemies are free to flee and lay traps
Yes, the rogue is powerful. But using his power might be tactically unwise, putting the weaker party members in danger if the enemy is not outnumbered from the start.
If the party is outnumbering the enemy, chances are the enemy itself is pretty strong. So the rogue still has to run the risk of getting smacked because he needs to go close. And he does not have the staying power of a warrior class.
So the answer to the implied question of "how to balance this power": you need smart enemies. Enemies that employ tactics. If they just stand there in line, waiting to be slaughtered, then the rogue is overpowered. Let them be smart, let them exploit the tactical weaknesses of the rogues somewhat egoistic power.
And in the end of the day, the rogue would not be able to do a sneak attack if not for the warrior (or anyone else) standing next to him. So the warrior should get some credit for that damage in your group, too. It's a tactical decision. Sure, the guy with the football in the endzone get's the photos and headlines, but in the end, it's the team that wins or loses, not the single player.
Best Answer
Spells cannot be used for sneak attacks....
... unless the spell involves making a weapon attack as part of its action, such as Greenflame-Blade and Booming Blade, in which case, you can apply sneak damage.