Good n Evil grips are excellent
Oury grips IMHO are even better (You can get lock-on versions of the Oury's in the UK from Si Paton)
But as others have said – check your riding position. It's possible you are a bit too stretched out. (It's also possible you are gripping bars too tight)
I had similar problems last year. Overcome by:
1) Using gloves with pads. But try/check before buying as 90% of them have pads in wrong place ie the pads don't come anywhere near bars when you grip em, so total waste of time. NC-17 work for me but expensive… and quality is 5hite. Pearl Izumi also seem to have pads in right place but don't seem to make nice MTB gloves.
2) Using bars that have more flex/give like Azonic DW Revenge as opposed to stiff ones like DMR HT Wingbar
3) Loosening my grip on bars during hard climbs
4) Shorter cockpit (move seat forwards)
5) Moving hand position MUCH more often on long climbs
6) Doing more riding after making the changes above
It's completely gone for me now/at moment.
Have a google/read about Carpal Tunnel Syndrome and check it ain't that (check what part of your hands go numb ie which fingers). Persevering through CTS is not a good idea as it can make it a lot worse.
I don't rate the Ergon grips and I personally found the theory/science about their design unconvincing. I also found they got in the way when you try to drop your wrists on techy climbs, and they made it harder to grip the bars on rough descents – which for me made it worse. (Having said that…they may work for you)
HTH