1 STR/MND adds 1.5 damage to cloudsplitter. 1 CHR adds 3.3 damage to primal rend. Primal is always stronger because of it, since you would have to get your STR and MND together to more than 2.2 times larger than your CHR.
In normal melee gear (which has a lot more STR and MND than CHR, thanks to the fact that it's 2 stats vs 1) Primal Rend does more.
In MAB gear and STR/MND for Cloudsplitter and CHR for primal, Primal rend does more damage than cloudsplitter.
With elemental WS atmas, Ultimate/Lion/Blinding horn for cloudsplitter, and Ultimate/Beyond/Baying moon for primal rend, primal rend does more.
Perhaps while brewing cloudsplitter might do a little more due to 2 maxed out 999 mods compared to 1, (though with no dINT comparison, I doubt it) but killing 3 nm's at the same time with aoelian edge beats using a stronger WS anyway. In any other situation, primal rend is stronger.
And aftermath doesn't exist. Do you know how many times I've gone the entire duration without it procing a single time? 30 second duration, with only a 30% proc rate, and only on the mainhand is negligible. It doesn't even make up the lost damage from rampage, much less beat it.
Yes, and your normal hits are doing far less damage as well, so the double damage procs do far less damage. The numbers remain unchanged. Rampage always win, by a mile. If cloudsplitter is winning for you, I'm going to have to say your rampage gear is terrible.The 1200+ rampages outside abyssea are not on anything close to an even match. if you want anything EM or higher, Your rampages will not often break 800. They certainly don't AVERAGE 1200. Whereas the magical WS will be consistent.
Believe me, I tried for weeks to convince myself I didn't just waste months of effort getting a farsha, but I did. There is no set up inside or outside abyssea where cloudsplitter is more useful.