Can someone explain weapon stats?

[Phoenicia]

..but if you DO stack a ton of it then your defining limit on DPS is your TP regeneration, so there is essentially a soft cap on usefulness.

Not only do you run into the TP issues. Skill speed 'should be' at a soft spot so it allows GCD/oCD synergy. It can throw off the timings. Such as having Life Surge up every 2nd(?) Full Thrust. I am not sure about DRG new rotations since mine is among 4 non-60s. But at 50 I remember if I had too much SkS (and I did) it would come back up near Chaos Thrust and would sit on CD for a while 5 to 6 GCDs till I got to FT again.

Other examples would be WAR wants just enough to fit 9 GCDs within Berserk duration. On NIN if I have too much SkS I run into mistiming B4B and Duality later on in my rotation. Basically I delay B4B slightly and use it before an Aeolian Edge at some point and ~17s later 'supposedly' get to Duality another AE while B4B is still up. Too much skill speed and I will either have B4B fade before Duality CD is back up or reach AE before Duality is up (or both). NIN also runs into major mudra clipping MORE off the GCD issues with more SkS.