Just played a game with a number of issues including low fps and missing health bars

I loaded into the game as malzahar and couldn't see my healthbar or anyone else's (I could click on character models to see their info, still, so I went with it). Then about ten minutes into the game, my screen froze and I couldn't alt+tab or ctrl+alt+delete, so I forcibly shut my laptop down. Then I powered it back up again and after some windows updates (maybe this is a cause?), I loaded in to the game to find that I could see health bars this time, but I was experiencing incredibly low fps (1-5 fps). I restarted my computer once again to find the problem persisting. I changed all of my video settings to very low and turned off shadows, and my fps became about 20 for the rest of the game. What the hell happened?