There are literally 0 reaction feats.
1 scan: He got blitzed.
2 scan: He didn't react to that blitz. On the first pic, after he got sliced in half, we can see that Obito doesn't have any tags on him. It was later, when Obito stopped and 'posed', Tobirama somehow managed to tag him.
3/4 scans: Lol. That bomb was there for like 5 panels, Minato managed to think of what he should do, Sasuke managed to push Naruto away - they didn't do anything about that because, you are right, they were in awe. Tobirama was somewhere else and I'm not denying his analytical and calm mind - that's why he rushed in. There's no reaction feat here, since in the meantime many thing happened. And then, it was just a simple FTG. Moreover, it was all off-panel, we don't even know where he was prior to jumping to the bomb.
5/6 scans: Lol, u call it reaction feats? God Tree didn't go after Tobirama at all, so he was watching the whole situation from the beginning. He saw Naruto being caught so he threw his Suiton. Where is that reaction feat when he was aware of the whole situation all the time?
Having said that, it's not like I'm saying Tobirama is slow or has bad reaction feats. He's good in both fields, but to me Orochimaru is still faster AND has better reaction feats (not counting FTG ofc - it's not speed after all).