TBH, that's actually not really the situation - or maybe it was one of the situations and there were actual multiple times pacov split top against a massive wave.
The actual situation (in which Rammus called you out - after already asking you to group a few times) was this:
1. The enemy had just gotten dragon, not your team
2. Your team was fresh from base, the enemy was not, having just tanked baron and presumably wanting to shop.
3. You walk top, to get a pretty huge wave. You ult dragon to see if the freshly baroned enemy team was there. Your ult doesn't hit anyone, but it also shows your team that no one is directly around dragon.
4. Your team starts up dragon and gets it, but then gets collapsed on (4v4?) against a stronger team and dies.
Your team was trying to make a play. Timing is always difficult when the enemy gets baron, but trying to """trade""" baron for dragon is a very common strategy for losing teams (even moreso once the dragonbuff thing comes out), because just sitting in your base isn't how you're going to win. Let's compare it to the patented "suicide split" for an inner or outer tower (i am going to disregard inhib/inhib tower suicide-splits since those are usually responded to much faster due to homegaurds and thus are much harder to pull off successfully):
You are almost certain that you are going to die, you "might" get a tower. Best case, you delay 2/3 people and waste a minute of baron. Worst case, your team gets dove under inhib tower and die 4v5, lose the game.
Generally the losing team is able to secure the dragon. Best case, you get the dragon and escape with zero deaths, effectively getting the team 1,000 gold and denying the enemy 1,000 as well. Sometimes someone dies, but not always. Worst case, your team dies 4v4, and you lose the game.
That's actually objectively better than a "suicide split" because it's possible to get a much bigger reward (a 2,000 gold swing versus a mostly "useless" T1 or T2 tower worth 500 gold). Even though it's possible to get near-aced and then lose the game from there, dragon is the only time your jungler/support is going to get any gold for the next 3 minutes while pinned inside your base against the baroned up team. The risk is pretty much: "get gold to maybe get a comeback or lose a game we were already losing 3 minutes faster". Versus "get 500 gold for the team (maybe) and waste 90 seconds of baron for 1-2 members of the enemy team, then probably die and give the enemy ~300 gold".