Nothing wrong with the social life. It's what you make of it.
The Aston social scene is somewhat smaller, in that, I cannot walk accross campus without seeing one, two or three people I know. Its quite a close knit, tight community.
The guild events may be hit and miss, but frankly, Birmingham as a city has more than enough to offer. Broad Street, the canal district, the Arcadian, China Town, The Custard Factory and now Oceanea offer you plenty of night out opporunities.
In regards other social events, Aston has plenty of sports and other societies that are well organised and diverse in nature.
In the end, Aston has everything you need to have a fantastic social life, you simply have to get yourself about and get yourself involved.