The rootfs is compressed and /var/lib/dpkg is mostly text files so compresses very well, when I moved it to /home I only gained about 10MB. When doing it I didn't notice any slowdown with the app manager, but I didn't think to benchmark, so there could've been some I didn't notice, but why would moving files from a compressed to an uncompressed filesystem cause a slowdown?
And why exactly do you have 2GB swap? If your apps need that much the constant swapping would make the device unusable, even the default 768MB is excessive.
It would be interesting to read that thread where you originally read this to see if there were any conclusions as to why, if it isn't close to being full the only thing I can think is fragmentation. With your rootfs at only 67% I shouldn't think any slowdown is being caused by lack of space.