As Dexter hasn't gained much size/weight in the past 15 years, I doubt that he has upped the dose that much either.
Also what really paid off for him in the long run is that he never played the size game. Never bulked up heavy in the off-season, always maintained a low bodyweight year round, plus easy pump training on machines and cables instead of heavy compound movements.
I could be wrong, but Dexter could be on as less as 2000 mgs of total gear/week, regarding his bodyweight and height. Also I doubt that he's a heavy slin abuser, never got that crazy full 3D look like a Phil or others.