One thing you have to be careful of, mostly when working on internal tools, is that you don't end up building around the idiosyncrasies of one particular person. This is something that actually happens in some places.
I actually find "bottleneck" a nicer word than "blocker" here (although not sure if "nicer" is what you are going for). I really like building for humans and the only times I've ever truly felt excited about being a developer is when I've had direct contact with my customers. It can be very trying, but the payoff is always nice.