I'm not sure the 60D is more robust than the T1/2/3i, just bigger and heavier. I know people with Rebels (not specifically those models) who put them through hell and they always come back for more. Rebels have a very small and light form factor that suits many people, especially those with smaller hands, and with lightweight lenses mounted they make for very light - and durable - camera systems. Mount a heavy lens on a Rebel and the balance might start to feel a little odd, though there again it's quite manageable and it depends what you're used to. Choose whichever feels right in the hand and in the pocket, but don't let fears of longevity (or a lack of) influence your judgement.
There are many people who justify their D700's by saying they're more solidly built than a 5D2. I think that's nonsense. I have never heard of a 5D2 suffering from lack of strength or build integrity. The D700 is an amazingly heavy beast though, significantly heavier than the 5D2, but I regard that as a negative, not a positive. My own setup (5D, 7D) is about as heavy as I feel comfortable with, and often that's also just too heavy and gets left at home.
Canon 5D & 7D (both gripped), 24-105L, 100-400L, EF-S 15-85, 50 f1.8, Tamron 28-75, Sigma 12-24, G10, A1+10 FD lenses, tripods, lights etc