Yeah, I don't know anymore either.
Brain moles are 1 RHD magical beasts, whose chassis is a mixed bag (tiny size, low land/burrow speeds, okay dexterity and wisdom, terrible constitution/strength/intelligence, weak bite weapon, free weapon finesse).
Their special abilities amount to spreading a psion-only disease that takes a day to incubate (how often do you fight psions in melee range that then go to live on for at least one more day?), an immunity to location-detecting magic, and some PLAs.
Said PLAs are... moderate. Detect Psionics is reasonable, Power Leech is kind of okay if you fight low-level psions a lot (removing 1d6 power points and healing you for 1 HP is an okay use of an action) and terrible afterwards. 3/day Aversion is okay control, but not stellar: the same goes for Mind Thrust.
Ideally, a brain mole could make an okay wisdom-based caster or manifester. Compared to jermlaines, who already fit that niche quite well, they have worse (much worse) stats, no limbs, and none of the rat-related abilities, but some pretty useful psionics as well as a burrow speed.
However, -8 intelligence hurts. A lot. Entering prestige classes will be difficult, skills in general shall be sparse, and let's not get into the possibility of enemy casters carrying Ray of Stupidity. This, combined with the lack of limbs and inability to function in nearly any class, leads me to conclude that this is best rated -0.
I'd like to emphasize though: the brain mole can be quite good in the few classes that suit it, but it'll probably be inferior to a 'normal' race (with the possible exception of lower levels, where its upsides are more pronounced and its downsides less relevant).