Prison and Crucible are small enough that you can easily do without the HoL, especially on a fast character.  Also, on Crucible, if you're playing as Erebus or if you have a Warp item, you can hop across the gaps directly from the center to your base.  Higher levels of bat swarm make it really easy, but the 15 yard warp from rank 1 or from one of the warp items (Warpstone, 5500g, Cloak of Elfinkind, 12000g, and Cloak of Night, 2000 favor, Generals only) can do the trick with some practice.

If you don't lose HP, then you probably don't need the HoL.  A good Regulus or Torchbearer can kite enemies around half the map without ever taking a hit.  For them, +mana regen would probably help survivability more by keeping them going longer.

Also, buying priests from the Citadel can substitute for HoL healing to some degree.  If you stick with your priests, they can make life much easier.  Ditto idols.

You forgot to mention that at least two heroes - Torch and QoT - can drain their mana with REALLY incredible speeds (esp. with favors - -20% cd anyone?). And I found out that HoL on these heroes is the cheapest thing that can end your permanent OOM state. Healing is just a bonus here.

While I agree with you in principle, I do disagree on a few specifics. 

I cautiously agree.  Normally a Vlemish Faceguard and Scale Helm in conjunction is enough to meet a character's mana needs.  If it isn't, however, I find the heart of life is a better investment than upgrading to those of those extremely expensive helms.  It's in the same price range, and offers you a versatile tool.  You don't always want it, but sometimes it fulfills your needs just right even if you do have other forms of healing available.

If those flags are being held by an enemy demigod, heart can be critical for flushing him out.  After you beat them the first time in battle, they'll run back to their crystal and charge up while you're trying to take the flag, meaning you basically have to win two fights in a row against the same demigod (and this is before we even consider flag locks...) to actually capture it.  Heart allows you to regenerate while he's regenerating.

I totally agree about the unclean beast.  Don't get heart if you're up against him (unless you happen to be Oak).  I disagree about Regulus.  Snipe has a fairly long setup time, so if he starts preparing to snipe the moment you activate your heart, you'll still get most of your health and mana back before you actually get hit.  In fact, heart has saved my life from snipe a couple of times by giving me just enough health to survive it.  I'd also disagree on Rook because the trebuchet hitting you is something that doesn't happen very often.  It might only happen once every five or six times, and that's an acceptable fail rate for an item this good.

HoL needs a nerf, you shouldn't be buying the same item in 90% of your games if you can afford it.  Once everyone has caught on and everyone has it in every game it's going to seem more nerf-worthy.

Im with liq3, I buy Plenor and Vlemish every single game, and have no need for HoL (as Sedna). Even with other heroes, you are choosing between being able to run away and come back healthy, and being able to actually stay in combat longer. Sometimes you want to run away and come back, sometimes you want to stay in combat, the heart of life isnt OP because it doesnt help you much in combat.

Have you actually played anything more than a 2v2/3v3? In a 4v4 you'll get nuked by 4 people at once. HoL wont do shit against that, but buying 2 sets of armor will.

In fact even in a smaller game you may not get to use your HoL. It's not going to save you from getting mined, MotB, then nuked/stunned by some other character, or being chain stunned by an Erebus/UB duo. or about a million other combinations that happen if you're playing with any level of coordination/skill.

You should consider Blade of the Serpent as a favor item. One Circle of Fire/Ice Storm (is that what it's called?)/Ground Spikes on a creep waves refills your mana bar. You'll never need potions again and you can pump your money into something more useful.

I never buy HoL and have been doing fine. I rather have Platemail of the Crusader. The problem with HoL is that there are many ways for experienced players to prevent effective use of HoL. As a result, there are better ways of spending the 4250 gold.

It's an assassin only favor item, in the top left corner. It gives +dmg and has an ability that you activate and it gives you 75% mana leech (i think) for 10 seconds. Completely gets rid of any mana problems on high dps or area of affect demigods, i use it all the time with regulus.

lol; I was completely unaware of the assassin/general specific favour item menus

Well, now I know about them.

Take a look, did a large guide, blade of the serpent included, with screenshots even

http://forums.demigodthegame.com/350605

Nonetheless, I agree with you, I feel that while Heart of Life is fantastic (particularly with Oak) there are some DGs it isn't as useful for....plus the fact that you can't use it in combat is a huge detterant for me and I rarely ever buy Heart of Life.  

I mostly play Sedna, and usually if I get HoL it's not for the health regen, it's for the mana regen. Frankly, it's too versatile for the cost. It should probably be separated out to one that's only health and one that's only mana, or drop the extras from it entirely

Hmmm, it seems the cheapest way to get +15 health from items is about 2k (There might be something cheaper than 550+1500 (which gives some +max health too))

+50% mana, is worth at least 600 (which actually gives +35%), scaled up that gives about 900 worth of value.

So for the passive stats alone, it's worth about 3k... Without the active ability. Which is effectively a non-disposable potion* (If out of combat, but at 2-3 sec casts are the better potions really usable in combat?) which alone would add up to about 700 each use.

I think it needs to lose some, probably a nerf to the passive stats.

It seems like as soon as I start using HoL, every trebuchet and angel on the map comes for me. A huge number of my HoL uses have been interrupted by these 2.