Deep Gnomes as PC's

[DeathMetal4tw]

Are they overpowered?

[Svipdag]

If by deep gnomes you mean Svirfneblin, then yes they are more powerful than usual PC classes. This is indicated by the fact a svirfneblin’s CR is equal to his class level, rather than class level -1 like other races.

[Remco Sommeling]

If you want to play or allow deep gnomes in your campaign, you might consider replacing the first (or first two) level(s) to be a level in an NPC class.