I think I found sort of a cure for speed Rages, berserk or not (it seems to work against dual-wielding power Rages with axes & maces too but the evidences so far aren't too many). It still needs some testing and possibly fine-tuning but so far the results look promising - two of my Wars - two-handed and polearms - now win some 80% of the fights against speed Rages which previously took them out without breaking a sweat.
2H Rages are still a problem though...