I'm not sure what you mean by rock climbing in them?
The mixmasers are great for winter mixed - but above -5C I'd maybe go with a summer weight pant and fleece. You wont find one pant that does winter and summer well.
They are about as warm as a pair of R1 tights, but a little cooler then R1 tights and a pair of plain nylon pants overtop.
If your looking for winter soft shells then get a winter pair. I would not mess around with anything less then powershield though. But dont use them in summer, IMO even the stuff used in the Gamma MX's would be much too warm for most spring-fall use.
As for unlined softshell's? IME they are alot like expensive nylon pants, and nylon pants are cheaper and more windproof when it counts. I like to use them with silkweight or R1 tights all summer, and with the R1's all winter.
Last summer I did use a pair of the expensive Arc'Teryx Tweve pants climbing in the Canadian Rockies and I have to say that light nylon is my faverate for spring to fall use.
They are windproof (softshells tend to only cut the wind), they are amazingly quick to dry, cut the wind very well, and they have kept me far warmer and drier then the Arc'Teryx pants have. I think that's because the Gamma AR pants are much more porus. I do like to nikiwax my nylon pants though, and use gaiters with them when on the glacier. Provided their well cut you should not need any stretch for climbing in them.
The mixmasters ARE better for the winter then nylon pants with fleece tights (and better too then the thinner unlined softshells and fleece, IMO) but it's a close thing.
I should add that I use winter softshells from about -3, -5 C on down and fleece tights with the Gamma AR's down to about -7C.