I'm in the same boat as the person quoted - With almost 4k hours in-mission time with 46,1% of Valkyr Prime usage, and somewhere around 39,6% with regular one, Valkyr is essentially the only Warframe I play and changing her too much might really break the game for me. Don't judge, haha. 😛
In terms of changes, Warcry is perfect and my to-go, staple ability with Valkyr. But, that said - I think it'd be neat if the Warcry enemy slow-debuff wasn't just upon casting, but like, the area of range, as you move. That way, Valkyr could gain some small crowd-control capability. It might need some balancing to not be over the top, but it'd be an interesting thing to play with.
Paralysis seems to be rather lackluster ability. Wouldn't mind replacing it with something entirely different to add some synergy to Valkyr's kit.
Hysteria - Ehh... not using this much personally. I used to utilize it as quick self-heals, but with Operator's arcanes, I rarely ever need to do that anymore.