I was rethinking about the role in diablo 3. I think there are RGK, mob clearer, solo pushing, speed farming, def buff, attack buff, grouping, dragging.
RGK: build like heaven fury, shadow impale they should have damage mechanism that stack over time, or a mechanism that deal increased damage to a single enemy or first enemy hit.
Mob clearer: build that got mechanism whichscale damage with mob density. A pain enhancer is an example of it. Archon, spirit barrage, death nova also have a mechanism that scale damage with monsters. Build like star pack, work by using area damage, so in theory, skills that got a large area of effect could also be buffed to become Mob clearer build by stacking area damage.
Solo pushing build: build that good at both mob and boss killing. Usually, it damage multiplers are flat, and does not affected by mob density.
Speed farming: build that got screen-clearing effect or build that can attack while moving. They are also accompanied by fast movement. GOD DH, WOTW bar and POJ Monk belong to attack while moving. Multishot, WOL belong to screen-clearing build.
Attack/defense buff: any build that provides party benefit to other members.
Grouping build: build the excel at pulling a large group of monsters together.
Dragging build: build that can drag elite and move
Wild effect: There are also some builds that got wild effects, such as leapquake, Uliana, DOD, Jade. They hold a special role in creating diversity.
I think the 5 sets of each class should each take up one of these roles, there could also be hybrid build got element from 2 builds.
Barbarian:
IK HOTA should buff to become RGK, as HOTA has a small attack area.
IK Charge got scaling with mob density, but its area of effect is too small. It will left some monster behind. So it can only become a solo pushing build.
Reakor 6: based build couldn’t become RGK, as it usually only attack during COE cycle. So it should become a solo pushing build.
MOTE leapquake and Seismic slam: both builds got large areas and could become a mob clearer.
WOTW is clearly a speed build and should become one.
Frenzy bar is the current RGK build, but this will be overlapped with IK HOTA build. Perhaps, we can make both builds into hybrid build. Frenzy build would also provide defence buff to party and HOTA could provide attack buff to party.
Crusader:
Blessed shield: got a mechanism that scale with density. Should become mob clearer. The currently blessed shield bracer clearly contradict it.
Condemn: got grouping function and the dps is not bad. It can become grouping and mob clearing hybrid.
Blessed hammer: got item that deal damage to first 3 enemies hit and also got an item that increase blessed hammer damage per enemy hit by falling sword. I suggest picking a side to make it into RGK or mob clearing.
Shield bash: also got a mixed identity, shield bash itself deal extra damage when hitting fewer enemy, but shield glare change it into an AOE skill. However, this gameplay mechanism is fun so maybe we should keep it and make it a solo pushing build.
Sweep attack: it also got grouping ability and the area of effect is larger than condemn. Compare with condemn it is better at dealing single target damage, as it attacks speed make the band of the stricken stack faster. It also does not require at least 3 mobs to deal damage. So it should become an all-rounded solo pushing build.
Invoker and Heavery fury are both RGK build, perhaps we can make them differ from one another by giving defensive party buff to the invoker.
I would also suggest enhancing crusader dragging ability by buffing steed change.
Demon hunter:
GOD: speed build and best build for DH, it is overpowering compare to other builds.
GOD entangle support: 150% increased damage and group capability is hard to pass. It is becoming an essential build in 4 man meta.
Shadow imaple: one of the RGK option, can use a sight buff.
Rapid-fire: This build got a stack up time and a random area of effect, it could become an RGK build. However, this build will always have lower mobility compared to shadow impale, so I think it should provide another form of benefit.
Multishot: got good speed and large area of effect, could become either a speed build or a mob clearer. I think we should pick a side and buff it.
Embodiment of the Marauder: Sentries fire secondary skill remind me off trap assassin build in diablo2. It is fun, but it turns the set into pet build. So the current iteration of M6 is focusing more on the active attack part. I hope we can change it back, as this playstyle is different from other DH build. In terms of function, M6 can become mob clearer that provides defensive buff.
Want to post this part first, I will keep working on other class.
Let’s see make Diablo 3 so un-fun to play everyone quits FTW? What are you guys trying to accomplish?
finally! 
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