Anyone ever heard of or worked with this group? They are offering to help us find benefits for a WWII era vet, and I was wondering if they were legit, or if we should just DIY

Don't know anything about them but from looking at their website it looks questionable.
Any organization that wants to take payment from you benefits is one to avoid. Generally this is done by taking a percentage of back pay.
There are several free veterans service organizations that do a great job. I am not a Marine but a friend put me in tough with a contact at the Marine Corps League and they helped me sort it out. I know there are others as well.

I've heard of Patriot Angels, but, to be honest, I can't remember if I heard good things about them or bad things.
As far as getting help with getting benfits for a veteran, The American Legion, The VFW, and/or The DAV ALL have Veteran Service Officers whose sole job is helping veterans with claims. If the veteran you are trying to help is a Marine, you can check with The Semper Fi/Americas Fund. (Americas Fund is for Non-Marine Veterans)

Hope this helps. Good Luck