^ I don't think the fights against Thompson (6'5) and Wach (6'7) were boring at all. He wa also very explosive against Pulev (6'4). The fight against Joshua (6'6) certainly wasn't boring.
He had terrible stinkers against smaller opponents like Povetkin, Ibragimov and Haye (all of them around 6'2).
I think it's about styles, not size.
Styles make fights ...prime Mike Tyson vs. Wladimir would be a very interesting scene ...Riddick Bowe vs. Wlad would be interesting ...Muhammad Ali vs. Wlad would be something to watch ...all of them (Tyson, Ali, Bowe) have different heights.
Same goes for his more offensively minded brother Vitali ...even though he's more offensive, it doesn't mean it's a good fight ...if you let him have his way (Sam Peter, Cris Arreola, Shannon Briggs), he's going to slap you around all night long and it's not a good fight at all.
If you can be slick against him (Odlanier Solis until his body let him down) or take the fight to him (Dereck Chisora), then we have a fun fight.
It's about strategy, ability, styles.