Valde hasn't been OG's best player this whole year so far neither is ISSA an unproven over him when he has a great rating on LANs. Besides, Valde has played support role before.
They should have started off with Issa's bench/replacement rather than NBK but now they have gone down that path, they have to shift the roles. Just getting another support won't do them good because that wasn't their problem. Their star players are inconsistent, they need a heavy hitter.