make yourself some new macros that use /target shaman01 /cast heal

Use F1 - F4 or something and have a different target for each.

Whatever you do, the focus macros will always have slight delay

I suffer the same problem as you, but i've not bothered to do the above solution yet. Will probably do at the weekend. The best thing to do is get a guild mate to come heal you, tiz what i do