True, but he one upped those feats. He beat Majin Buu! Lol, but in all seriousness, good point, however, Yusuke did in fact have a small amount of spiritual power at that point, on top of the fact that he didn't really do anything effective against Gouki.
The 4 beast dodged lasers too. Does that make it lightspeed? Also more powerful doesn't = faster. The Genki Dama is probably the strongest technique outside the movies. But it's not as fast as most attacks in the series.
Mihawk stomp Don? That seems a little too extreme to me. In my opinion Mihawk and Don are the #1 and 2 Warlords respectively. Also with that recent feat of when he was going to bifurcate Sanji in half, his cutting rope extended pretty much from Green Bit to Punk Hazzard. His cutting power could be near equal to Mihawk's, plus he has more total abilities due to his devil fruit I would presume. I think Mihawk would have a very hard time against Don but as he is Número uno in my opinion, he'd come out on top.