You can also, if so inclined, make a macro with each first step skill (HT ID TT) that is:

/macroicon "accatck"
/ac "Mercy Stroke" <t>
/ac "Attack" <t>

This will save you the slot for MS and will mean it's always used almost as soon as it's available. (you'll never be more than 5 seconds behind).

Also suggest putting life surge in a similar macro with FT as it will get put up while you are mashing waiting on the gcd.