Fragmentation looks to be your issue. It's just going to keep getting worse until you update fw or HDD erase.
Apparently OCZ and Indilinx have collaborated to make a custom Vertex fw that pretty much will keep the drives in as new state.
Indilinx may post a fw update for the other manufactures but I doubt it will have GC like OCZ's. It may work differently or you may
have to wait for trim to be enabled both on the drives fw and on your ICH10R.