For simplicity, I'll refer to action boosts (e.g. Haste boost, Damage boost), "clickables" (e.g. Pally past life, frenzy, death frenzy), and "clickies" (e.e titan grip gloves, eardweller, madstone) collectively as "activating buffs."
The benefits of activating buffs:
As far as casters are concerned-
There aren't many to use. A caster is interested in a few damaging spells, and thus uses only 2 or 3 clickable items to amplify their damage in a certain spell.
The ones that are used have a very good duration. Superior freeze 8 that is available on a ToD belt is 3 minutes long. Even the eardweller is a solid minute of 100% extra damage amplification. Refreshing it isn't on ones mind all the time. Very manageable.
Their uses add dynamic to the game. I find it more interesting to have items that augment my efficiency.
As far as melees are concerned-
Activating buffs have the potential to skyrocket a melees performance. If all of the activating buffs available to us are used at once, a melees damage output increases MUCH more significantly than if the melee would swing without any.
Activating buffs provide dynamic to playing a melee, otherwise autoattacking and afk would be the gameplan.
Their use is directly proportional to melee player skill. Their limiting nature enables players to think and reason the usefulness of each activating buff, especially between long intervals of shrines. This is a benefit, because a melee is so much less useful when no activating buffs are used, gauging the times when your usefulness is most meaningful is a hallmark of a skillful melee player.
The detriments of activating buffs
Activating buffs have no difficulty check counterpart. Casters have activating buffs that are solely responsible for their damage output with their spells. There is no activating buff in existance that augments their DC's.
This is the fun one.
Firstly, the major activating buffs that melees depend on are typically damage boost and haste boost. These are the most powerful universal activating buffs that every melee wants to fit in. Fighters and rogues acquire tier 4 haste boost. Barbarians acquire tier 4 damage boost. Fighters and rogues acquiring both damage boost and haste boost via half elf racial perk achieve huge improvements.
And these very buffs that melee depend on to excel are 20 seconds a buff, are not self-renewing, such as paladins smites are, and exist in a typical quantity of 8-12, which is ~10 for your average melee with a moderate investment into their boost count.
Furthermore, in order to acquire that boost count; the fighter action boost line, for example, is worth 2, then 4, then """""""""6"""""""" ap for a single increment in a 20 second boost. Halforcs have it better, their racial line is 1, then 2, and then...still """""3""""" points for the same boost benefit that the first, 1 ap enhancement, provided.
A branching issue from this is the time. My fighter acquired so many activating buffs that I spend more time enabling them than I do swinging at a boss, and, its not even that many. Using haste boost, damage boost, and a pally past life clicky, and then a titan grip clicky is already pushing it, but...
Heres the key that diminishes melee effictiveness even when they want to amplify their damage as much as possible:
Activating buffs that are of the same type, outlined in the beginning as "clickies" are on the same universal cooldown timer.
I literally need to wait an entire cooldown timer for activating a different clicky each and every time. If you add these up, you have madstone rage, titan grip gloves, pally past life clicky, haste boost, damage boost, then maybe divine might if a paladin, frenzy, death frenzy, rage, if a barbarian, and even some characters acquire the rogue past life activatable for 10 extra SA dmg.
When the majority of those activating buffs are used, you actually lost a TON of damage output because of the TIME it took to do that.
Activating buffs are an amazing way to add dynamics to a players experience. However, their uses between melees and casters are, yet again, in great favor of casters because they don't rely on activating buffs to be effective as melees do.
The most powerful activating buffs a melee has, haste boost IV and damage boost IV, are limited, extremely expensive to acquire gains in, and aren't self renewing.
Furthermore, they are the most powerful abilities that melees have, and yet, are still largely ineffective when your friendly casters are cleaning up the instance.
Extremely powerful activating buffs should be provided to melees that enable them, when used, to have efficiency comparable to a casters for at least the length of their duration.
Activating buffs that are gear based need to be placed on separate cooldown timers for separate items. Activating buffs such as the rogue past life need a faster animation, it is very slow and costly to use time AND feat wise.
A barbarians rage needs to regenerate over time as well. It is useless to have a barbarian that has ran out of rages for the remainder of the quest. There need to be some recourse for melee activating buffs.
Those are my thoughts on this issue. Thanks for reading.