SEO is an overrated mystic factor that is often overhyped
Submitting to 4000 tubes is ridiculous. We've used Chameleon's Tube Submitter but dropped it: what makes sense to submit to needs/deserves manual submitting anyway.
I believe only tubes with content partner programs worth submitting.
I also believe that using over-watermarked videos on content partner channels is the biggest crap I've seen nowadays. Submitting over-watermarked videos makes no sense to me, at least my company works totally otherwise.