save or spend heroic

I saved up 10 heroic souls and 1 legendary soul to try and get NOTB eddie. Well I got super lucky and got him on my first pull. So my question is, should I use my 10 heroic souls to try and get one of the 4 star toons, or wait for a different rotation of toons and which toon should I wait for? At this point I think I have quite a few powerful eddies and am looking for other toons. Main eddies I use are BBE, Doomsday, Iron and now NOTB so maybe good toons to pair with them.
Also is there a place to see the rotation in heroic souls?
thanks!

This might be a late response, but a good rule of thumb is to save excess souls for a good chance to get something you actually want.

In the upper right hand corner of the game click on the unrolled parchment. This shows the monthly events and such. Usually it has three seasons of heroic rotations, but it is currently missing after last night's update.

The heroic rotation is up for me in the news section