the real problem with melee splash..

so you use melee splash for clearing maps sure fine... but for a build to be endgame viable you will need single target damage.

now generally if you play caster or ranged.. there is always a support gem that you can swap your aoe gem for in endgame content boss fights:

inc aoe -> conc effect
gmp -> slower projectiles

this is true for both on hit and even more true for dot builds, since both of these are double dip gems.

here is the problem... what the hell do you swap melee splash for? there is literally 1 shit choice ( added fire ) for phys builds which has absolutely no effect for dot builds...

introducing shitty treshhold jewels and increasing melee splash aoe won't make melee splash more desirable to build around...

Can use multi-strike, It you aren't using it already?

Or have a blue socket that switches from inc aoe → conc eff?

Yeah, its multistrike.

melee dam on full life if you have decent leech/lgoh, bloodlust if you do some skill alternating, life leech..

any red support, to which there are quite a few for melee champions

if you're already using multistrike then you can swap melee splash with melee physical damage.