Tobirama can probably counter Amaterasu, I think.
Amaterasu is the highest and the strongest form of Fire relase which could even burn fire itself.
My theory:
Amaterasu is simple Fire release + Uchiha spirtiual chakra + hate(optional) to make it stronger. If Amaterasu clash with normal water release then even with Kisame's amount of chakra Amaterasu could overpower water release and burn through it.
Maybe Uchiha's spiritual chakra cause change of color Fire release has, changing it to black and filling it's so much power at the same time, which cause this black flames to increase it's temperature, burning rate and all.
However Senjuu clan are known for having very powerfull full of life physical chakra. I can even go so far to say that is their Senju full of life chakra and skills in all Ninjutsu, Genjutsu and Taijutsu make Senjuu clan so strong, that it.
That why I believe Tobirama as the second strongest of Senjuu clan could counter Amaterasu with his water release,
if he would generate and put his full of life chakra into that water.
CONDITION: ONLY IF TOBIRAMA HAS FULL OF LIFE CHAKRA OR CLOSE TO HASHIRAMA 
Yang element - full of life chakra Senjuu clan posses
Ying element - powerfull spiritual chakra Uchiha clan posses
If someone from senjuu clan could have yang element as strong as Uchiha's Yin element or even stronger then in case of Tobirama, his yang element and Yin element inserted in Amaterasu could cancel each other, cause Amaterasu to loose it's mystical power turning to normale Fire release and then we have Water release > Fire release.
In short:
Tobirama - water release filled yang element
Izuna(if he has amaterasu) - fire release filled ying element
Only if Uchiha
user of Amaterasu has too much hate , then maybe Love of Senjuu clan would be needed to counter
lol
This should prove
Tobirama could counter Amaterasu according to my theory of course.
I believe that Tobirama could use
normal water release or
yang element filled water release. That why it was said that Tobirama is the best user of Water release, because none you suprass his yang element filled water release, unless someone was Senjuu and powerfull as Tobirama(imossible).
That exacty my thoughts
EDIT: To back up my theory about Senjuu's full of life chakra, let's compare Yamato and Hashirama, both posses wood release, Hashirama's mastery maybe be better than Yamato's but anyway that was Hashirama(Senjuu chakra) which make mokuton so powerfull in compare to Yamato. Even Captain Yamato say that thanks to Hashirama chakra inserted in crystal on Naruto necklace, he was able to stop him from transforming.
