from personal experience <mo> macros tend to work better as I can heal from the party window. If you add <t> or <tt> to the macro after <mo>, it will default to you sometimes and usually at the most inopportune time. If you want a more reactive heal that is going to hit your target without having to click go with <mo>. I just move my UI around to where my party window is at the bottom right hand side of my screen and move my buff/debuff bar right above it so I can keep an eye on Rot timer. I had an issue where it was auto defaulting to me before I just left <mo> and now I don't have this issue.