SassyTheSasquatchlootOh wait, I thought you just meant the words Critical Hit weren't appearing. It sounds like your tf_weapon_(name).txt files might be doing that, same way you get VTF crosshairs or no explosion smoke scripts. Have you recently installed anything like that or changed your hud?
When I shoot my rockets theres no trail just the rocket head, so yes I think to your question.
Go to C:\Program Files (x86)\Steam\steamapps\common\Team Fortress 2\tf\custom\(folder name)\scripts and see if there are a bunch of files named tf_weapon_(weapon name).txt, if so try deleting them (back them up) and see if that fixes it
If not then see other suggestion about amd drivers - you should be able to find them through here. I personally am using a driver from August 2015 and it seems fine.
You could also just launch the game in dx9 and see if that fixes the problem, it would show you're on the right track