Figured I'd post a little update since I started playing. I'm in Act 3 now, last time I played I didn't get beyond the start of Act 2. I'm following a build guide I saw on youtube that looked interesting. Tectonic Slam is actually pretty much the exact same skill as the one I was thinking of from Torchlight 2 except it goes in front of you instead of all around, but it still feels really good to use. It even uses charges similar to engineer from TL2, but right now my only method of getting them is from the warcry.
I also noticed that I pretty much haven't needed to use mana or healing potions except near the start of the game (and in some surprise situations with a really hard hitting special enemy). I wonder if the game is easier or if this build is really that tanky... or maybe I'm just overlevelled... It seems most people play the game by nyooming past a majority of the enemies but I have a habit of killing everything that comes at me. I'm not really in any rush.
It really depends. When your DPS is so high you vaporize most enemies before they stand a chance of killing you, there's no reason to have a ton of health potions. If you watch the L33+ streamers, they'll have maybe 1. And the other 4 will all be buff flasks.
However if your build ISN'T that hot, you will need at least a couple health pots. If your build has no real effective health regen (life on hit, life on kill, life leech, regen/sec, various healing from Warcries or consuming charges of this that and the other thing, etc...) you have no real way of regaining health. Which for most enemies in the game, prior to the final act, isn't a big deal.
But the last....few bosses in the campaign, and most bosses in end game maps, do a fuck load of damage. I'm talking, even on my tankiest character with the most HP and damage mitigation, a good crit will, if not kill me outright, take 90% of my health.
That's when you need health potions.
And the higher you get in maps, and the more dense the enemy packs get and the higher their monster level gets, that damage can also all add up very, very quickly. I'd say around T9 maps, the total spike damage from a pack of Champion enemies can easily be as dangerous as some boss attacks. More so, depending on the specific enemy in question.
So like most things in PoE it's a matter of the balance of your build. Fuck loads of damage and little HP or damage mitigation? Chances are you won't survive many late game hits to even get the chance to use a health potion. On the other hand, damage not so hot but a shit load of mitigation and HP? Chances are you will need those health potions as you chip away at high life enemies and bosses, because even with a crap load of HP, PoE on average tends towards dishing out a lot of hurt at the higher levels.
Bottomline: don't judge the performance of your build or the balance of the game until you've beaten it. Because almost all PoE players get a rude awakening around the 80% to 90% completion mark of the campaign. Enemy damage goes up up up, and health goes up, and many build are not prepared for the sudden spike. Which is why the best advice for new PoE players is to focus on a big life pool, because it makes that transition from the campaign to the end game a little less painful (or demoralizing, depending on how far out of whack your build is.) Many people just max out damage through the whole game because they don't see the danger or the challenge of enemies, and then *BOOP*, they cross this magical line in the campaign where the enemies are closer to end game difficulty and they suddenly go "my build is fucked."
FWIW, when you run into Kitava for the first time, that should be your signal that the game is shifting gears and going to get harder. If you find the first Kitava fight difficult in the slightest, start planning on re-prioritizing your build based on what didn't go well. (Was getting one shot, swarmed by normal mobs and slain, fight took 10 minutes because your damage was so low, etc...) If you breeze through the first Kitava fight with no real problems, just pay attention to the kind of hits you start taking from later bosses. Because by the time you fight Kitava the 2nd time, you'll basically be at starting map enemy difficulty, and if you're struggling there.....it will only get harder.