There was a Kunkka player in my team today. He was sporting an Octarine Core as his first major item after Shadowblade. I'm aware that Tidebringer damage does heal him, but is that really worth it?
He could get a Heart of Tarrasque for 400 gold less, or a Satanic for 50 gold more.
no, it's a great ultra-lategame item on almost any hero who even slightly relies on spells, but getting it on kunkka before even crits? that's just a bad idea. bottle into crystalys into blink in daedalus is the general hit-n-run build, where you stock up on rapiers and ohko lategame, phase boots into shadowblade/crits/rightclick items is the no-blink build where you fight a bit more manmode is also pretty popular, and either of these builds could benefit from an octarine in the right situation, but not as an early game item.
Octarine does a few things:
gives nice +25 Int - next to useless on kunkka early game, you can manage mana with just bottle + treads.
gives +hp and +mana, both of which are nice, but as said before, urn/bottle early game will let you restore/conserve hp/mana until later.
some +hp and mana regen, nice but as stated above, not entirely relevant early game.
then the good parts:
cooldown reduction. as it's %-based it benefits both high and low CD skills, either giving them more uptime or making them more spammable.
it gives -2.5s on torrent (not too useful overall.), -1s on tidebringer (bringing it to 3s CD from 4, this is good because of the extra procs during fights, but with only octarine that extra damage wont do anything, a crystalys would give a lot more DPS at a LOT less cost), -2.5 on xmarks, and -10s on boat.
the cd reduction on boat is very nice, because it goes from '40s cd spell' to 'once per creepwave spell' allowing you to defend highground or push into the enemy very very well, but overall this isn't worth the 5000+ gold until you're breaching base, and even then, ship + pipe/crimson guard would be infinitely more useful for pushing highground.
the other good part of octarine is spell heal, a 5man boat will heal you for somewhere around 600hp, and a 1k tidebringer crit on 4 people will heal you for 1k hp. but with JUST octarine, this means nothing, that 100~ damage to 5 people will be arond 100hp of heals, sure you can do it once every 3 seconds, but literally any other item will give you more survivability here.
TL;DR, terrible choice for a first item, nice lategame in certain situations.
Like any item, yes, it can be worth it in some situations.
Suppose Kunkka absolutely needed to spam torrent and boat as fast as possible, maybe to defend against megas, or the game is just being very teamfight-oriented.
Suppose Kunkka needs to gank the other lanes non-stop because his team is losing them and he doesn't have time to go to base to regen, and the runes are too dangerous or even mined.
I personally would not buy this item on Kunkka often, if at all, simply because of how much it costs. I would imagine there are usually better items for Kunkka for similar money, but...it could be worth it.
I feel Octarine Core is made for heroes like leshrac,qop,zeus etc, heroes having multiple spammable spells.
Kunkka doesnt have as much spammable spells, I guess the CD reduction for boat is cool, but i would rather have more damage or positioning items(blink/shadowblade). I would get a fast Drums/BoTs than go for an Octarine if i really want mana. With new X he is similar to an Ember spirit pretty much.
Also I personally dont like satanic, but heart works out well on kunkka. My favourite build is phase, drums, shadowblade/blink, crit, bkb/mkb depending on game, rapier.
