As of current, this skill is used as a 1 pointer to clear thrash mobs, for cannon-based or WDPS STR based builds.
It has a 1 second cooldown, and a small AOE on proc. The proc only happens with WDPS skills (and of course normal attacks) only.
Coup de Grace only procs on stunned enemies, which is the main problem since Elite, Hero, Champion and Boss monsters all have stun resistances (with bosses having very significant resistances).
Unless stun mechanics can be reworked, the most immediate solution seems to be to change the proc conditon of CdG.
- % based
The most obvious, and boring. (although, stun procs are %based too......) I think a potiential problem with this is that CdG scales incredibly well, and this may make it a little too strong.
- procs off Shocked targets
Basically, Lightning Brand. The Engineer has several lightning based skills, so this is a good way to throw it in.
- has a chance to proc off the Charged Bolts that Shocked enemies release
Not sure if this is do-able, but it would be kind of cool, although we'd be back in to square one with "sucks against bosses".
- procs off Slowed targets
The Engineer has a bunch of slowing abilities (Onslaught, Immobilizing Copter, Shield Bash to name a few), so this was a natural option, right?
- procs off Crits
The Engineer isn't the Berserker, so... well I'm iffy about this one. Just throwing it out.
- has a % chance to proc for every condition the enemy has
A little generic, but this would include Stun, Blind, Immobilize, Freeze, Shock, Burn, Poison, andddd basically any buff. (IIRC, the Engineer has a multitude of buffs)
Alternatively, Coup de Grace could be a passive enhancement skill.
Whenever the Engineer uses a Charge, the next attack will proc a Coup de Grace, dealing Electric damage based on your STR. (with internal cooldown, of course)
- or -
Whenever the Engineer has full Charge, the next attack will be a Coup de Grace, dealing Electric damage based on your STR. (with internal cooldown, who'd guess?)