rb133c has less memory than rb133... I wouldn't recommend you use it as an Access Point
I think i bought a few rb133c before you anounced them on site.
They are all L4. 4 of them are doing wds on 5 ghz and they are doing just fine, with few mb's traffic, continuosly.
The others are put as ap, with routing, not bridge, and each handles between 15 and 30 clients, with no problems so far. All of the rb's have r52 or r52h on them.
So, it does not seem to me that it is sooooooo slow.
You get what you pay for. In this case, even more.