What heroes should use these items. The only hero that comes to mind is zephyr.It makes sense if your going to jungle and are going to take damage from the neutrals.
Otherwise, its not useful in team fights. The regen will not save you or help you kill anything. It doesn't help you lane, since you shouldn't be taking damage from creep waves. The only decent item you can make out of it is ruined axe, which no one should really buy(there are much better dps items).
Is it just for pub/low level play?
Just remember if you're going for sustainer that the mana regen is entirely percentage based. If you have low intelligence, this could amount to no more than 1-1.5 mana per second.
It builds into Sacrificial Stone which, though nerfed, is still a very useful item on certain heroes (most notably electrician).
Ohh yea sac stone. I guess I was thinking more along the lines of agi/strength.
Don't forget about Runed Axe as well, which requires a sustainer. It greatly improves farming ability
+ its a very usefull item for int heroes and the mana regen for str or agi heroes is always welcomed
I believe it's an ingredient in the Restoration Stone. Thus, Tempest/Kotf/etc. could get it.
That being said, Runed Axe is pretty trashy, and I wouldn't recommend it on very many heroes. You will generally find it on heroes with innate crit, such as Swiftblade/Madman, because the splash ignores armor, and slash crits can do severe damage to the other team.
In it's new form Sac stone is good on a few heroes, Blacksmith/Elect come to mind.
^ power supply and some blight runes always seems to be enough for me and is a lot cheaper.
What I'm trying to understand is does that work in competitive games or is sustainer decent?
Sustainer is a superb laning item.
Problem? People stop laning at the 15 minute mark, and you're unlikely to field the sustainer before that point (or if you do you neglected +stats, boots, or any other part of your core).
That's why most people skip it.
It helps in early game if you are being harassed. It also helps you use skills to harass a bit.
However, don't get this unless you're gonna build runed axe or sac stone.
Depends on your hero too.
Some heroes, like DL and MB need the lifetube for runed axe/hotbl asap. Since these kind of heroes usually have fairly poor lane presence they will need to survive and last hit as much as they can, so then lifetube is basically a rushed item.
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Depends on the hero you get. Those with decent attack speed should get helm first so they can follow up and turn it into a whispering helm. Shamans headress is superior to black helm ( vanguard ) in every way for tanks. Pers for those mentioned above who tend to want to build runed axe (bad item =x) or sac/restoration stones.