I don't think it is so clear cut.<@Alhuin> Is Vampire mode Tsukune stronger than Moka?
<@Arkangel> Lol
<@Arkangel> Fuck no
<@Arkangel> I'm not even sure if he's stronger than Moka's younger sister
Tsukune's punch is at least as strong as Moka's high-kick. I think that physically, he may be stronger than Moka. Her aura makes her very strong, but Tsukune has already displayed strength that surpasses her on a few occasions. Where he falls behind is technique and experience. That alone has made Moka very strong. Kokoa on the other hand is similar, she only has super strength to her benefit. She's pretty weak as far as vampires go. Tsukune is definitely stronger than her, since they haven't bothered to limit Kokoa's power in any way (both Moka and Kahlua have limiters).
If you had to rank the characters in terms of useful combat ability (ascending scale):
Yukari
Rubi
Kokoa
Kurumu & Mizore (they always fight together now)
Tsukune
Kahlua
Moka
Akuha
...
...
Sun-sempai
I tentatively put Akuha above Moka from what we've seen, but they still mention that Moka is fairly rare among her kind. Her silver hair marks her as a super vampire, far stronger than the average vampire. However, Akuha exhibits the same skills that make Moka stronger than Tsukune: technique and experience. She obviously surpasses Moka in that by a huge margin. Sun of course is stronger than anyone in the series. Unless the opponent assassinates her outright from a distance, Sun would destroy her opponent before they even realized that combat had already begun. They showed that even Moka would easily have died at the hands of the other siren if not for Sun's protection, while Sun had been attacking from the very moment she began to defend.
Lastly, there is a key thing that makes Tsukune stronger than most vampires, he is still human. He has none of the associated weaknesses, and most of the same strengths. If they fought in the rain or another body of water for instance, Tsukune could effortlessly defeat Moka, and would likely have quite the advantage over even Akuha. Her martial arts skill would still be a factor, but it is tough to fight when perpetually subjected to electric shocks.
(Fong is a complete wild card, so I don't think he is rankable yet. I also did not count in Kurumu's illusion attacks because we haven't seen their effects on vampires for an accurate comparison.)