tl;dr
When I take off an Explosive affix on my Vacuus Scipio bow, and replace it with a socketed Endow mythstone to get +50% Weapon Dmg, why don’t my Multishot and GuidedShot DPS numbers change? The item stats DPS goes up, but the offense stats page stays the same…
Bump.
Seriously? Please?
Bump, I guess.
Inconsistencies in visual coding? Maybe. 
did you notice any damage increase with your multishot and guided shot? if yes, then its just the stat page with a bug. if not, then it might be a bug with endow. either way you might want to report this in the bug section.