I don't use wrecking blow on my nightblades, kinda feel like it's a cheese skill, but you do well with it regardless. Glad to see you're having fun with the stamblade and doing some good 2vX.
Right, I also prefer not having the cast time that WB needs. Basically the same reason I originally got away from being an archer back in 1.4/1.5 with snipe's casting time.
I use ambush/surprise attack myself. The guaranteed crit from charge (and slightly lower stam cost) is tempting, but opening from combat from stealth and getting the empower from ambush is the way I prefer to go.