I agree.
Two of the teams above us, City and RS have worse keepers than Robles. Possibly even Cech who is nowhere near the GK he used to be.
Robles all round game has improved this year but I still think he falls behind the top keepers in shot stopping and distribution. We do need to replace him at some stage if we are to consistently challenge top 4 position. But we have other area's that are a bigger priority as you say. Plus, at this stage, I doubt if we could attract a really top established keeper anyway.