In what way does he die mid-game? Are you always using his ability, and thus keeping his health a little on the low side? I'd recommend only using his ability when you have a fair amount of beasts and/or they have a lot of human characters, particularly if some of them can be taken out.
Matriarch might also be a good card to use, and possibly run in command so that you can potentially move Hermit to support to have him heal, especially since his health will have gone up thanks to Aleta, Caretaker.
As far as other suggestions, Granthar, I'd think warrents being in maindeck. He's got a nice effect when he enrages, and is pretty beefy. He's also hard to dodge when you play him off of opponent's initiative. I'd also run a full set of Pack Leaders, but that's probably personal preference considering I like making my characters really beefy. It might not really be needed with Hermit.
Enraged Hulker isn't really that good of a card, I've come to find out. Sure it can enrage and become bigger than a One of Many, but that's throwing in another 3 resources and getting out less stats than two One of Many with no other additional benefit. It has it's uses, but in a game where single target removal is fairly prevalent, I don't see it's benefits really working out. :/
If you DO go with Pack Leaders in the main deck, I'd also recommend throwing in Word of Command as well so you can push them onto the battlefield immediately and give a surprise buff to everything. Even without, Word of Command is a rather versatile card so might be worth running in main regardless.
While kidnapper is a fairly good soft removal card, the fact it's human tends to pose a problem in this deck. Still, it could be played like an extended Controlled Temporal Anomaly to rest stats of an opponent's character so I guess it could still see a use.
Currently, Rabid Rabbit doesn't do well with Pack Leaders (or any kind of buffs) considering it loses it all when it transforms, and thus having it out with Pack Leader causes it to be weaker overall, if it even survives when it attacks.
I do hope this gets fixed fairly soon. On the other hand, it's also a low cost character and Hermit decks tend to try and flood the field for massive buffing so I guess it could stay just for that.
Hermit decks usually don't need ramp as much, but that doesn't mean it doesn't help. Still, if intending to run Untapped Wilderness, if you don't have multiple copies of the card, it might be helpful to at least have a way to tutor it through Cartographer or Explore. The downside is that both these cards cost as much or more than the location itself, so that means you won't have the ability to play the land as fast if you don't have multiple copies regardless. You could also consider swapping it out for Corrupted Forest since that buffs your attack and lowers your opponent's attack (except in WP mirrors). Just an idea to consider.
Verore and WP have a pretty good combo together with Lightning Blast and Track. This combo essentially lets you kill any target for a fairly low cost. The downside is it takes two cards, but I think the benefits outweigh the cost, not to mention humans can also be instantly killed with Track and Hermit.
These are my personal thoughts on the deck, being an avid Warpath player, but I will admit that I'm not really considered a top player and others might have better advice for you. Still, I'd like to think my advice holds at least some weight as I have won my fair share of games with Warpath.