I do the exact same thing, I turned off errors in chat, but it still shows errors in the middle of your screen. The times when it displays the error "target out of range" it will just cast on you instead so you have to watch the error being displayed. That's the biggest problem with that macro settup is telling if a target is in range. Other times is when you raise a target, it takes forever before you are allowed to actually heal after his/her health shows up. Line of sight is the other error you have to watch out for but you will still cast on yourself.

I've been thinking about taking the <me> out of the macro and see if I get better response from it, but haven't tested it yet... don't know why lol. Every now and again I get the latency issue where there is no reason I should be healing myself but I do >.> but its not that often.