As I indicated in a couple of posts upthread, the rules currently do allow this for a wizard. Is that a problem?
I have never seen an arcane spellcaster with no combat-relevant spells. I have played several with no damaging spells.
I dislike damage spells as a spellcaster since anyone can do damage, so I'd rather do something they cannot do, ideally with spells that stick around for a bit rather than needing to cast another each round.
I sketched out a spell selection sequence for a wizard, up to about 10th level, that leaves a wizard with no damaging spells, and no combat-only spells.
Is sneak attack "combat only"? It can take out an unwary guard, facilitating exploration (or kidnapping to facilitate interaction). Regardless, can we
please stop using "damage only" and "combat-useful" interchangeably? Damaging abilities are a subset of combat abilities. Not all combat abilities are damage-causing. I can even envision damage-causing abilities that
are not combat abilities (eg. a slow poison inflicting 1 damage every hour, which cannot be healed until it is cured, is pretty combat-useless, but could be useful as a social - intimidation - context.
To reiterate "does damage" and "is combat-useful" are not the synonyms.
Of course a rogue needs to be versatile and more powerful with level. But as the wizard example shows, there are ways to do this without defauting to assassination/back ally mugging. Why can't we have high level rogues who help win combats by blinding and confusing enemies; by concealng the rest of the party so they can launch devastting ambushes; by charming and bluffing and persuading NPCs; by leading the party away through secret paths that evade enemy forces; etc? Fantasy RPGs like Burning Wheel and Hero Wars/Quest can support these options for rogues - why should D&D limit them to casters only?
Blind/confuse seem like
excellent potential replacements for sneak attack. Concealment to ambush is borderline - is that ambush as devestating as, say, a Fireball because you get the drop for the first round? If not, it is still useful, but less than a full replacement. The rest seem like great non-combat abilities for rogues (or others, for that matter), but do not replace the ability to be effective in combat. The other option is to make combat a much less frequent challenge resolution mechanic, that occupies a much smaller proportion of game time, so being combat-useless doesn't take the player out of game for hours, but maybe only a few minutes at a time and rarely, if ever, for 25%+ of a game session.
Or we could stop insisting that D&D is a tactical combat simulator, focus more on the fact that D&D is a role playing game first and foremost, and stop describing a rogue doing less damage per attack than is optimal as "campaign destroying".
I'm open to this just as soon as we have a best-selling, well regarded adventure series which features less than 25%, by volume and time spent playing, of challenges resolved by combat, where that rogue with not just "less damage than a rogue optimized for combat", but "no combat abilities competetive with the other characters such that he is a non-issue in combat" is not only viable, but a desirable character.
Earlier it was suggested if a wizard finds they need to do more damage, the DM can insert a scroll of a damage spell into treasure. And that same DM can't insert a magic shortbow for the rogue? Or it was said the wizard can choose a damage spell at a higher level - and a rogue can't select feats that increase damage at a higher level?
A scroll provides the wizard one more choice of spells to cast. A magic shortbow that replaces the ability the rogue gave up? Great - I'll take the noncombat ability plus the free magic weapons that return my combat ability, rather than the combat ability and no non-combat ability. Adding a new spell, or a dozen new spells, to a wizard is trivial (unless Next changed that a lot - and my understanding is one L1 spell can be used for all spell levels, with increasingly powerful effects). ThirdWizard nails this one dead on.
The Rogue who trades away Sneak Attack at 1st level for, say, better interaction skills can take what, exactly, that will bring his combat skills back up? If the Next rules provide for him to do so, I would be much less concerned with his loss of combat ability. But if the real answer is "well, he can retrain to correct his stupid decision when he's up four levels", my question is why not just prevent the stupid decision in the first place so the player doesn't spend four levels bored and useless for a good chunk of the game?