Q: Is there any way in increase the power of procs?
A: Yes.
A proc is cast as if you are casting the spell/skill at that level.
Any bonuses it would get were it a skill, it will also get as a proc.
(read: Synergies if available, +% spell damage, -%enemy resists, clvl.)

I believe the difference in "on striking" and "on attack" are related to melee and ranged attacks. I believe that "on striking" will work with ranged attacks (such as firing a bow) whereas "on attack" only applies to melee weapons.

Not positive about "when struck" or "when hit", but it could be a similar situation where "when hit" only applies to "when hit with a melee attack".

A bit of testing between the 2 items would probably illuminate which is which if you want to give it a go.

_________________
People who live in cinder block houses can throw whatever they want.

Q: What triggers 'on Attack' procs?
A: On Attack triggers every time you swing a melee weapon at an enemy. (Swinging in the air does nothing.)
Bows and throwing skills don't trigger 'on Attack'.
Note:Apparently, non-'Normal Attack' skills require a successful AR check.
(Thanks terryys.)


Q: What triggers 'on Striking' procs?
A: On Striking triggers any time you actually hit a Monster with a weapon-damage carrying attack.
This includes multi-hits from skills like Retaliate, Wychwind, Faerie Fire, etc.


Q: What triggers 'on Kill' procs?.
A: Weapon carrying attacks or poison attacks that take more than 1 frame to kill their target.


Q: What triggers 'when Struck' procs?
A: When you get hit by a physical attack.
Shield-blocked attacks don't count. Avoided/dodged attacks don't count.


Q: What triggers 'when You Take Damage' procs?
A: Like it says. This includes anything other than damage over time from poison or life drain.


Q: What triggers 'when Attacked' procs?
A: Any melee attack, regardless of whether it hits or misses or you dodge it.

its from a FAQ from another d2 mod called median xl. you could google it. its pretty fun to play and practically everything is changed from the original d2. but it has very different gameplay as compared to hell unleashed. it requires little strategy, basically its just shoot and forget and enjoy the pretty colors.

http://modsbylaz.14.forumer.com/viewtopic.php?t=7291

here's the link. most of the info should apply to hell unleashed. this mod is soft coded, so all the hard coding from diablo2 remains.