List of non high tier champions that will suffer from DFG removal.

Diana. DFG is really important to getting her snowballing, and as every Diana player knows... If you don't snowball your prety fucked. Getting a too late zhonya's means losing the game. Veigar. DFG Q R on AP squishies is the only reason to play this guy amirite? Mordekaiser. Hextech & DFG are to core actives for him to make sure he gets his ghost. Annie. Midlane annie's core items are DFG mobi boots, allowing her to utilize her great roaming and snowball, she needs to as she tends to be outranged in lane. Katarina. I have some problems seeing a new Kat build? Hextech Gunblade instead i guess? og the full MPen build, but DFG removal really hurts her already not very good dueling, and removes a lot of in-lane threat. Malzahar. burst malzahar rushes DFG void staff for some of the best 1-shotting in the game, that's now gone. AP Shaco. Ap shaco is highly reliant on DFG to amplify box traps dmg.

Those are the champs i think need to see some changes to help them after DFG removal, feel free to add additional ones i might have forgotten

Edit: DFG removal also removes a lot of AP offbuilds such as AP nunu, AP Malphite, AP Poppy, AP Rengar, etc. because they're reliant on DFG to amplify high base damages, or some ludicrously high scaling on a single ability.