Medivh gained a lot from his trip to Draconia, his training with the dragons broadened his horizons about mana in general. The correct way to chant a spell , the correct way to cast , he learnt everything from the dragons , and had a massive improvement.
However , none of that compared to the job Rudra entrusted him . Medivh always knew he was a valued member of the Elites. Just like Rhino was the leader of tanks , he was the leader of mages .
Ofcourse it was a prestigious position and most of the guild members looked upto him , but he was not elder level inside the guild. His reliance was always limited. Hence when Rudra approached him with such a herculean task that was the core of the power of the Elites for many years to come , Medivh was naturally taken aback.