The chief pilot criticised my rotation rate as being far too slow (in his opinion) and warned this could compromise obstacle clearance with engine failure.
Bad science! It's a cost/benefit analysis between lower obstacle clearance (1% of take-offs are first or second segment obstacle limited) VS running the speed on one engine too low (100% of take-offs with an engine cut at V1 are at risk of this problem)
If your rotation is too low - energy is still being added from the engines, so if you see a tree in the window, you have that energy still available to pullup.
If your rotation is too fast - well, the closest a normal flight EVER gets to the stall is at rotation, and stall, flip, crash, burn, die is the classic.
If you are TWO engines, then you have so much extra power over the ONE engine case the performance is planned on, it's not a problem.
If you lose an engine, you will have less pitch-up inducing thrust, which will lower your rotation rate in any case.