Sounds like you've got the same issues as me. I'm a neutral runner, and if anything I actually under-pronate slightly, but one of my feet splays outwards ever so slightly meaning that when I push off I roll inwards a tiny bit on that foot. I often get a blister towards the front of my arch, which is partly due to rolling inwards on the foot. I wore Asics Cumulus for years and with every new pair of shoes, I'd trim a tiny bit off the underside of the insole with a Stanley knife, which helped a lot. That was before I realised what was causing it. My friendly shoe fitter (whose advice I trust totally) recommended that I go up a half size (7 to 7.5, but more about shoe sizing later) as arch blistering is also a sign of feet without enough room. It seemed to work...
I only found out about my foot splay very recently after years of running, when I developed shinsplints after running in worn out trainers. My physio said I could stick with neutral shoes but if the shinsplints continued to be a problem I should consider orthotics, but definitely to stay away from pronation or stability shoes, as my problem wasn't pronation or instability.
My shoe fitter pointed out how my old shoes were knackered even though the soles weren't too badly worn, as the inwards rolling had stretched the inside of the heel cup on one shoe, and he said I should pay more attention to replacing shoes when they got worn, keeping the old ones for shorter runs and wearing newer ones on long runs. I stuck with the Cumulus but also got a pair of Brooks Ghost to try, as the soles/heel cups are slightly more solid on them.
Your foot numbness definitely sounds like it could be due to small shoes. Have you got a decent amount of wiggle room for your toes? I found after a few years of running that even with the same make and model of shoes, I had to go up in size. I think running maybe makes your feet stretch out a bit over time. Either that or it's just that as you run longer distances and your feet swell a bit, you realise you need more space round your toes to be comfy. Whichever it is, I started running in a 6 as that was the size I wore at the gym, quickly went up to a 6.5, moved on to a 7 at the start of the year and for my newest pair of shoes bought a 7.5. All Asics Cumulus, so no variance in size due to different manufacturers...
Edited: 09/10/2012 at 11:02