Leech should be more of a melee life/facetanking focused mechanic in Path of Exile. Unlike path of exile orbs, ranged and caster leech is way to powerful, so it is hard to get.
On the other hand, life on hit is quite powerful on ranged imo. The new elder rings can have something like ~20 Life on hit each, which can end up feeling like pre-nerf vaal pact for ranged.
Of course, ranged leech is really easy to get, as long as you’re playing a Ranger or Duelist. Ranged leech requires very little investment, if you’re playing a Ranger or Duelist. All of the attack leech nodes work just fine for ranged attacks.
Additionally, there are many “melee” spells (Blade Vortex, EK nova, Vortex, Ice Nova, Shock Nova, Flame Surge, Lightning Tendrils, Incinerate, arguably Freezing Pulse due to its severe damage dropoff) where the builds utilizing them have to facetank just as much as a melee facetanker does – or moreso.
For typical tm ranger with avoidance based defence, maybe the leech is less useful than amroured ‘melee’ dude. Armoured melee can afford to have steady recovery rate, maybe you want to recover fast on your ranged dudes, which means instant flask at this point in game.
If your avoidance is good enough and you aren’t playing hardcore, you can most likely survive with just leech since even though it might seem like you get chunked fairly hard, you have more time to recover it since you’ll be hit less often compared to that armour-based tank that is soaking every hit even if at reduced amounts.
You even are better at dealing with elemental damage and most spells (if you have Phase Acrobatics or other sources of spell dodge) than that armour character, too. Plus, due to your range, you can choose to avoid a lot of things those melee characters cannot.
Spell leech near the part of the tree that focuses on spell damage and spell crit would be retarded… Spells are already amazing in their own right, you dont need accuracy or specific weapons since they scale off a lot of generic nodes. Adding is spell leech to the top of the tree would need to be gated by some kind of keystone that has a drawback since that would be so damn easy to splash into almost any spellcasting build.
Leech is a thematic element for both the duelist (mostly slayer) and shadow (see the claw implicits). It would make sense to have at least one leech mechanic up north.