How much memory does your MBP have? I imagine it's a 2GB machine and therefore is swapping like crazy. I have the same issue when trying to load modern web apps on my 2GB netbook. Setting up zswap improved performance a bit but then CPU became the bottleneck.

I have a 2008 C2Q Q9400/8G/SSD machine which is still used often, running Linux with Q45 IGPU. CPU load is low and it still has enough grunt to perform reasonably. I used it as a daily driver for many years and have never had an issue with web sites and basic office/dev work.