Yeah it was such a low amount I just assumed it was a flat boost like most other skills. 30% is alright, still nothing to write home about for a single hit skill - Cartar Stroke still has 150% scaling and 4 hits for a 600% scaling total, so it’ll almost always hit harder. Against a mob with 5 debuffs (say, crosscut, crown, armor break, cleave, warcry) you can hit for 250% with vertical slash which, on top of the base damage increase and extra 50% from cleave, will make it pretty reasonable for a c3 skill. HL3 is maybe worth it now?
Still not sure about leveling Cartar Stroke though. The charge time is still really long at high levels considering it doesn’t increase scaling or # of hits, just a flat damage bonus. If Multishot hit 16 times at level 1 nobody would put points into or charge it.