Should I hoard Ditto?

I caught 30 ditto's and transferred them all except 8 with decent CPand IV's.

I've caught 26 and have so far kept 6.
at first I was keeping the high IV dittos, but---
Should I only be looking at the Stamina number?
do the other two come (atk,def) come into play after it transforms?

Caught 14 and kept 1

Personally i can't really see a need to have one, let alone more than one. If legendary mons roll out then maybe on offense copying one of those will have a use. But even then why would I need 6 of them? Just revive/heal next time you hit.

Since it uses your stats won't make sense to use a worse ditto instead

Can't think of a single use on gym defense unless whole gym system radically revamped

Evolved one Wonder, kept one Wonder. Put the rest on Gyms and didn't revive.

I think keep a few, just for the entertainment value. One of the most fun battles I did was to battle a gym with 5 Dittos. This was shortly after Dittos appeared. So, as the attacker, my line up was: first mon 10 CP pidgey and then progressively higher pidgeys - like 100 CP for second pidgey, 200 for third, 300 for fourth, 400 for fifth (and then a Vape to be sure I won). So as soon as the first Ditto changed to the 10 CP pidgey, I switched to my second, etcetera. It was a very fun gym battle. It was like you were always battling your former self. And I won them all. I could see some use where you were battling a mon that was a great counter to the next defending mon in the gym. So you bring in your Ditto just before you kill the defending mon, and then you have a great attacker for the next defending mon. I will have to try that - just for fun.