Total size isn't what I would call bloat, that is features getting added that don't really have a security purpose for a security based application.
The windows Programs and Features and Add Remove Programs have been notoriously inaccurate in the past. In my Win7 Programs and Features doesn't even give a figure on winXP Pro is gives 336MB which is correct. But this figure will fluctuate as the defs folder contains the current VPS folder and the previous one, before avast does its housekeeping and prunes the oldest one.
Currently these virus definition sub-folders are 86.5MB, this gives you an idea of just how many signatures are in the database. So that would essentially match the difference between a clean install and one which has two defs sub-folders before avast housekeeping when it would drop by 86MB.
Basically your understanding of how avast works is giving you the wrong impression on calling it bloat.
As mentioned earlier, with today's Hard Drives; 300-400mb (whatever) is nothing. Just a hiccup!
I'm only running 60 GB HD and have never given 400mb a second thought.
Just saying.
