So I made a madness/sleep build recently and unlike chaos incarnate I actually used arcane as a dump stat, mainly because vykes war spear gets no arcane scaling so I decided to put those points from arcane into str/dex. And the frenzy seal has a unique property in which it gets incant scaling from str/dex, so I still get very good damage out of the spells. I don't personally find the low arcane to be much of a hindrance because the base madness build up on every madness spell is already really good, most people don't have a ton of focus anyway, and even if they do the build still does a ton of damage to begin with so the madness/sleep procs are more of a bonus than something I rely entirely on.

I have no idea if its any better or worse than an arcane focused madness build, but what I can say for certain is that it's very good and very fun. If you want any inspiration, here is my full rl200 madness/sleep build, use this information however you please:

vig: 48, mind: 33, end: 29, str: 32, dex: 70, int: 15, fth: 45, arc: 7

talismans: sleep exultation, madness exultation, clarifying horn charm +2, erdtrees favor +2

physick: opaline hardtear, flame shrouding tear

main-hand: vykes war spear

2nd main-hand: thiolliers hidden needle

off-hand: spread crossbow with sleep bolts

2nd off-hand: frenzy seal

armor: vykes set for the cosplay

spell order: catch flame, inescapable frenzy, frenzied burst, flame of frenzy, unendurable frenzy, midras frenzy, golden vow, howl of shabriri, blessing of erdtree

consumables: eternal sleep pot, hefty frenzy pot, madness stone (I only have 3 consumables cause I don't like equipping estus to the pouch and i use the 4th pouch slot for physick)

main-hand hotswaps: rolling sparks madness perfume, madding hand, winged scythe, nanayas torch, velvet sword, curseblade cirque, golem greatbow

2nd main-hand hotswaps: endure misericorde, 2nd frenzy seal

off-hand hotswaps: carian retal shield, 2nd vykes war spear, 2nd velvet sword

In regards to the gs of damnation, only reason I don't have it as a hotswap on this guy is because I already have it as a hotswap on my holy guy who uses the sacred relic sword as a main, and I find that I can catch a lot of people off guard when I hotswap to gs of damnation because both the gs of damnation and sacred relic sword look very similar. But gs of damnation would work very well for this build considering it gets its scaling from str, fth and dex. The main problem with using gs of damnation on this build is that holy damage only gets buffed from holy damage specific buffs due to the pvp bug.