Worth powering up an 89% Arcanine after the nerf?
15atk 10def 15sta and Fire Fang + Fire Blast.
I'd power it up in a heartbeat if it wasn't really low leveled. It only has 400CP right now and I'd have to spend a lot of dust and candy to power it up.
Answers
Arcanine is still a strong Fire type Pokemon, the biggest changes were buffs. It is slightly weaker than before, but nowhere near unusable. Lost 3 attack and 14 defence, or roughly about 1.5% attack and 8% defence, which shouldn't make much of a difference, if any due to damage rounding.
Flareon got buffed so that it's more in line to Arcanine than it was before. If you already have a Flareon and all you want is something to attack grass types with, then there isn't much need to power up the Arcanine.
If you don't already have another fire Pokemon, then your Arcanine is worth powering if you'll think you'll get use out of it.
Alternatively you could try evolving into a Flareon if Eevees are common where you are. Flareon's guaranteed a double fire moveset, so it might be less costly mass evolving Eevees than powering up your low level Arcanine.
You don't need to power it up, it's got a high level so it's usable as it is. It doesn't really matter that it's got low IVs either, because you're not going to power it up, so it's lowered max potential is irrelevant.
Since you already have a fire type attacker, what do you want the Arcanine for? If you just want to look cool when battling gyms, that's your decision to make.
It would take a lot of power ups to reach the point where the Arcanine would be better than your Flareon.
But if you were planning on powering up an Arcanine to max level anyway, the one that you have currently is probably the best one that you're going to get.
Well, the low IVs is the reason I don't want to power him up, so it does matter :P
I want an Arcanine because it's the strongest Fire-type pokemon in the game, and might remain so even after gen2.
You're right, this is probably the strongest Arcanine I'm going to get. I'll just wait until I can amass the ~100 or so candy needed to max him out.
In addition to the information already given, i want to state two things.
(1) Fire Fang deals just 20% more damage per second than amber. This makes Arcanine better than a CP-wise comparable Flareon. The best about that: It is not stronger, but quicker, making dodging easyer.
(2) I consider 2 of the 6 possible movesets of Arcanine useable. (Different to gamepress i would not rate a bite-moveset a or b, because i would like to have Arcanines unique selling point and this is fire fang.) Thinking this way, you sure can wait, evolve maybe one, maybe 5 nobody knows how many 90% Growlithe, spending 50 to maybe 250 candy just to get a comparable Arcanine as you already have.
You could (what i would prefer by far) just take this great arcanine you already have, and power it up. Yes, maybe you spend 40k more stardust, in comparison to a level-20-hatch. But: You already know that you have got the best moveset and (as stated above) save a lot of candy.