Cooldown is for bleed DoT builds like this. Bleed builds hover around 400-500% duration, so cooldown doesn’t matter, but total damage mods and crit damage do. It’s close to the best bleed skill in the game right now.
On paper, Blade Arc with the transmuter could make for a powerful Physical nuke as well. For example, this Warlord should be able to hit some impressive crits with it though I have never got the greens to test it properly. Someone can probably polish it further as well (like dropping 30-40 Physique points into Cunning for Crucible).
BWC and Judgment are both spells, usually maxed only by casters and they have huge CDR. Actually judgment can be spammed with the -CD modifiers. Blade Arc is melee based attack, usually works well with 2H weapon, which will often lack any CDR.
My experience is that BA is working with transmuter only with Bleeding damage, especially going Savagery Warder. Internal trauma is interesting idea, like your GT. But spam version is definitely better.