That's the exact build I was going for Dark And Darker Gold, but found it way more effective in solos. Fighter has terrible disengage, so in trios I found I was getting 2v1 bumrushed by their frontline a lot, and you can only realistically riposte one attack at a time. Plus low armor builds are terrible vs rangers. I could see it working w/ a frontline comp though so yo ucould actually get 1v1s vs their frontliners.
In terms of armor scaling, there is a huge movement speed difference between naked/shirt and say templar or dark plate (even gambeson tbh), but a very small dmg redux difference. Armor is only good if you get into 200+ total since the curve is really messed up.
The only armor worth wearing imho for this type of build is the helmet for headshot dmg reduction. The rest should prioritize movespeed and having ok-ish mr since hte beginning of that curve is very efficient (unlike armor, which is effectively the same in the middle range from 70-150 or so despite there being massive speed differences in this same range).
Crossy is very effective solo as well, especially in goblin tunnels, but it was bugged so I had to stop using it.
I've only done one playtest, but I'd say a heavy armor build w/ falchion/heater and recurve is best for trios. For solo the longsword/crossy build is way more fun and comparable to the tank build in effectiveness (unlike trios where the tank build generally is way better unless you cherrypick your comp).
I love that build, but in only works in trios w/ specific comps, it's fun in solos though. As fighter I'd go full light armor except for the head gear, or go full tank so you can hit the 200+ part of the curve where the dmg redux actually scales. Never go 100-170 armor since the tradeoff between physical dmg redux and movespeed is horrifically bad, you need to polarize your armor rating as a fighter. Also, it's not a coincidence that there was lowkey a naked meta among sweaty players this playtest, movespeed is op unless you're going full tank cheap Dark And Darker Gold.