Went through and tested it to hell. Victory March now caps at 600 total skill. Very easy to see with decent gear and Lv 85 skills.
Victory March caps at 600 total skill for 96/1024 Haste. (+2 Instrument adds +32/1024 making this total 128/1024 Haste. 12.5% Haste.)
What does this mean for the future of marches?
(Champion's March is just some fictional new march tier I'm using for the purposes of this post.)
Advancing March caps at 64/1024 (96/1024 /w +2 Instrument) [9.375%]
Victory March caps at 96/1024 (128/1024 /w +2 Instrument) [12.5%]
Champion's March will probably cap at 128/1024 (160/1024 /w +2 Instrument) [15.625%]
Right now the non-SV cap for marches:
Victory + Advancing = (128 + 96 = 224/1024 = 21.875% Haste)
Haste Spell + Victory + Advancing = (224 + 150 = ~35.5% Haste)
SV'd Victory + Advancing is exactly 43.75%, the Magic Haste Cap. (No need for Haste Spell.)
Currently +2 is the highest march instrument available. Assuming SE will release a +3 instrument in the future and hopefully Gjallar trials, the following will work:
Advancing March: 64 + 48 = 112/1024 = 10.94% Haste
Victory March: 96 + 48 = 144/1024 = 14.06% Haste
Champion's March: 128 + 48 = 17.19% Haste
Just to add: Lv 85 BRD has 560 total natural skill. You only need 40 skill from either merits or eq to cap. Pretti much any BRD can cap now, and next update every BRD will be capped.