As the primary guy here who enjoys Musou-style games, I thought I'd have an answer for you, but:
1. DQH had slightly more RPG and Tower Defense elements, the latter of which could get really annoying.
2. You already commented on Senran Kagura.
3. The last Dynasty/Samurai Warriors I played was DW7, and I have DW7XL, DW8, DW8XL, SW4, and Warriors Orochi 3 (Vita) in my backlog. For what it's worth, I really liked DW7 when I played it, and I've played almost every numbered Dynasty Warriors game (skipping DW6).
Pirate Warriors 2 is pretty good from what I remember, but you'll get more enjoyment out of it if you're a fan of the One Piece series.