At the time of this posting, some of the stats for the build on this site are incorrect (presumably due to calculating umbral mod stacking incorrectly). The actual power strength is 181, armor is 2047, health is 1070.
This is my current favorite Valkyr build for endgame. There are absolutely other ways you can build her, I have other builds I use for other situations (I have 2 Valkyr Primes built and forma'd) this is just my personal favorite way to build her as a Valkyr main.
Quick note, the arcane guardian I had equipped in the video was a mistake, you've got more than enough armor with umbral fiber and your warcry. Some people choose not to run umbral fiber because of diminishing returns from stacking armor, I personally like it as it does give a substantial increase to your effective health, and it amplifies the benefit from the other umbral mods.
This is basically a hybrid hysteria/warcry build, focused on tankiness. Its great for arbitrations, I've run it through a ton of them. You use your melee weapon to dps, and switch to hysteria (and invulnerability) if you're worried enemies could cc and do enough damage to kill you. If you're running low on energy in hysteria, swap to your gun and take some damage which will proc hunter adrenaline. If you low on health, either use a lifestrike/healing return melee or hysteria to get back to full.
Dying is only a concern at really high levels, and/or if you put yourself in a situation you shouldn't, like jumping into a mob of 20+ eximus buffed enemies outside of hysteria, and getting cc'd (and if the enemies aren't of sufficiently high level when you do this, they still won't be able to hurt you).
With weapons you have a ton of options for what you want to run with this. I ran a Krohkur to show off a weaker, less popular melee (you can get a riven like this very cheap) and for the fashion frame. Basically, with a status primary or secondary, you can run a melee weapon build for damage, pop condition overload on it, and 1-shot stuff. You don't have to run a hybrid crit-status build like I did in the video, a crit build is fine, you just need condition overload.
Sample Condition Overload Melee Build: https://overframe.gg/build/1050/
Sample Status Proc Gun Build: https://overframe.gg/build/1051/