I don't know what Classes tag Aegis adds, so you'll have to find that out for yourself.
Add a level of normal Aegis to a character. "Develop -> Enable Data File debugging", then "Develop -> Floating Info Windows -> Show Hero Tags" will bring up a window with all the tags on the hero. They are organized alphabetically by tag group name (shown in the left column), so scroll down until you get to Classes tags and look at the tag ID column next to that (the center column). That should give you the tag ID you need to apply as a matching CSCountAs tag.
Add a level of normal Aegis to a character. "Develop -> Enable Data File debugging", then "Develop -> Floating Info Windows -> Show Hero Tags" will bring up a window with all the tags on the hero. They are organized alphabetically by tag group name (shown in the left column), so scroll down until you get to Classes tags and look at the tag ID column next to that (the center column). That should give you the tag ID you need to apply as a matching CSCountAs tag.