Is it okay to use Unmend on bosses you can't reach?

Hey there, I was wondering something about DRK.
If you can't reach the boss, is it a DPS loss to use Unmend on it? I'm just a little confused because at first I thought it was bad since it uses MP (wastes Dark Arts) but then thought about the whole 2400 MP = 140 Potency thing.
Unmend is 150 potency for 480 MP, so again, would it be a loss to use it when you can't reach your target with your normal skills? Answer might be really obvious but for some reason I just can't wrap my head around it, I need someone to spell it out for me lol.

i guess it's a dps loss if you break your combo with Unmend (Hard Slash > Syphon Strike > Unmend > Hard Slash > Syphon Strike > Souleater...). also you have to be forced to stay a whole GCD out of meele range, otherwise you are delaying your next combo.

No uptime = no DPS. It's still beneficial to spend MP to deal damage if you are unable to reach the boss and it doesn't break your current combo if you can complete it a few seconds later.

Yeah forgot to add "without breaking your current combo" to the main post. But yess, thanks for the answers you two! Mystery solved :p

Think about it this way:

Dark Arts: 2400MP=140 potency (this is how 'most' of your MP will be used, and what would be lost if you used MP on unmend)
Unmend: 480MP=150 potency

If you cant use a melee combo GCD, then its perfectly fine. (say, running around the edge of the arena with black hole teathers in D4S and theres no way you could be on the boss for example). Ideally you wouldn't break a combo either. There is some magical tipping point where it would be OK to break the combo to unmend X number of times, but I don't know those breakpoints off the top of my head, but considering it would have to fit in the time where you 'could' have kept your combo in that ~10 sec they stay up, I find it unlikely the math works out in unmends favor. I'd avoid breaking combos unless it will be extreme downtime or the combo would fall off before you could use the next hit anyway.

TLDR:
*If you have 2.5 sec of downtime and your not breaking a combo, go ham on unmend.
*If your combo action would time out before you could use it, go ham on unmend.
*If you have to break a combo to use unmend, it would require some math to figure out how much down time unmend spam you need to break even just holding the combo. There may be some rare situations it would be worthwhile, but probably safer to just hold onto your combo most of the time.

Look, let's just be pragmatic and practical. Keep that GCD spinning, so spam unmend if you can't touch the boss. During OS4's exdeath's blackholes, tanks should be running around the edges and spend time away from the boss. Weather or not it breaks your combo, you'll have to step away. You can play it safe and step away as soon as you see the cast bar, and at that point you should be spamming unmend. You COULD risk it and stay until you finish a combo, but again, you should be spamming unmend as soon as you're away for at least one GCD.

learn your ABCs. Always Be Casting. Keep that GCD going!