I'm playing a character right now with Deep Impact, which is a psionic feat similar to Wraithstrike - it lets you expend your psionic focus to make a single melee attack as a touch attack. You can pick it up starting at 5th level, with one feat prereq (Psionic Weapon). It's a useful ability, but it's not gamebreaking, even with my beatstick of a gestalt fighter/psychic warrior.
The problem with Wraithstrike is that it's for ALL attacks in the round, including things like Cleave attacks, and any extra attacks you may be able to pick up. If it was just one, like Deep Impact, I wouldn't have a problem with it at 2nd level. As written, however, I'd never allow it in my games. I probably wouldn't allow it even at 4th or 5th level. I might consider one of two alternate versions, however.
1. A 2nd level, swift action spell that only affects one attack.
2. A 3rd or 4th level spell that isn't a swift action, that affects next round's attacks. This rewards groups with Spellcraft and cooperation, as the party's casters yell to the warriors, "Get away from that dragon! Something bad's going to happen if you don't!" It also requires more tactical play, as the character tries to set up a full attack against a target that might be aware of what's going on.