Per the EJ forum:
MM Shot Sequence:
Marksmanship
Priority Ability
1 Kill Shot
2 Chimera Shot
3 Arcane Shot
4 Aimed Shot
5 Steady Shot
Chimera is said to be the second in priority (it is assumed the you start with serpent sting). Unlike kill shot you can shoot chimera at any time (not restricted by enemy HP), but I would say it is not 2 in priority but should be shot when serpent is almost over (or enemy is about dead, whichever is first). It is almost a shot that is special and does not belong in a priority listing.
Is this correct or am I not thinking correctly?