Frankly, 4|5 for 2 is extremely OP, and your ability doesn't make it balanced.
I think it makes it plenty balanced. The most advantageous part of high damage-cost creatures is that you can rush. However, you can't rush with only 1 creature. In addition, most rushes will have creatures that have more than 4 attack (unupped) or more than 7 attack (upped).
I think this would work much better, and be easier to balance, if the Greater Good activated ability was discarded.
Horned Frog is a 3|3 unupped for 2
Elite Cockatrice is a 5|5 upgraded for 3
4|1 - 4|5 unupped is worth 3
7|1 - 7|5 upgraded is worth 4-5
I do not believe that Pride is worth a full -1 quanta cost so the stats selected should be from the lower end of the range and perhaps a -1 upgrade reduction is called for over a -2.
I would estimate 4|3 Pride, 6|6 Pride as being worth 2
|4
. [remember Light is meant to be CC resistant]