Ditto is fun to play with, but if we have limited stardust, I'd like to find out what benefits there are for powering it up to the max.
For putting in a gym, the best possible CP at level 40.5 for a Ditto is only 723, so if it is placed in a gym, when the gym's level is lowered and one Pokemon is kicked out, it almost will be Ditto to go first, unless there is even a lower CP Pokemon, which might not be very likely. So for the purpose of having a Pokemon stay in a gym for gym bonuses, a Ditto might not be that effective.
And what about if we use Ditto as an attacker? Usually we want to use type effectiveness to defeat a Pokemon, so we tend to use a different type Pokemon. Also, isn't it true that the HP stays at Ditto's own HP and is quite low, even when the Pokemon copied has a high HP?
Are there benefits that are overlooked for spending a lot of stardust to power up a Ditto?