The following scenario played out in a game I recently played and I'd like some input on how to handle it.

I'm playing Malphite at bottom. Trundle starts the game with me and goes into the jungle after level two. I am then soloing Malphite & Ashe at bottom while the rest of my team is laned up or in the jungle. Around lvl 6 and fight breaks out at top; three opponents vs Jenna & Taric. The pings start and keep going. I am tempted to leave my post at bottom and allow Ashe and Malphite to take the turret, which would have happened if I had left. I stay at bottom and hold them back on from the turret, but Jenna and Taric die. Should I have sacrificed the turret to go help my team? They certainly acted like that should have been my choice, but I feel like it was a losing situation either way.

If you are holding them off 1v2 at your tower, that means your team should have either a 4v3 at top tower OR should have a free push on mid with equal odds at top. Either way, as you were bottom and have a long haul to get there, you should have been the LAST person needed to make the haul over there. Your trundle should have been heading that way once pings came in and as mid was empty (3 top and 2 bot), mid needs to make the call to either free farm/push while they can or swing top to balance things out.

I'd also like to know how things went down up top. Janna/Taric is a strong team for defending a tower. You've got Janna's shield for the tower, her ult if things get dicey (assuming she was 6), and the rest of her soft CC, + Tarics heal and stun. That's an awful lot of kiting you can do around the tower even 2v3. In any event, if the tower was lost if they die, then they should have retreated before being killed. Backing down and losing a tower is bad, but dieing and losing the tower anyways is worse.

It honestly sounds like there were plenty of mistakes made among your team, but I don't think your decision to stay bottom (assuming your recollection of the events is accurate) was one of them.

Normally I would say you should always try to help out your team.

But no, there is no way you can go from bot to top if a fight is already starting at top. The two people at top are supposed to ward if they are going to push and if they do it, it is their fault.

A team with a jungler vs a team with no jungler is a different topic but imo the jungler needs to watch the lanes if the enemies do not have a jungler or else it feels like a 4v5. I'd blame trundle for not helping top and you gotta get used to this sort of thing as this will happen a LOT in League of Legends.

In a situation like that, you'd have to go from bottom all the way to the top and that's not worth it. It really falls into Trundle's hand to help out in the fight on top, or mid's choice to go top and have Trundle hold middle.