I bought GTA5 mid 2015 and finished the Story Mode without really getting into Online until a few weeks ago some buddies wanted to play it again.
I barely get 65-75 FPS with the lowest settings and I keep lagging out even when there is nothing big rendering.
I tried without any overclocking, it didn't change anything.
Even when my FPS is at a stable 70fps it still freezes dropping to as low as 0 fps and going back up again