I just had an idea that might make Eclipse more manageable and allows it to remain in the spec for flavor while still retaining a gameplay changing element. I’m open to feedback if there are potential issues with this idea.
What if Eclipse lasted indefinitely (removing the 15-second limit)? Then, casting Wrath meant you enter a Solar Eclipse, while casting Starfire entered you into a Lunar Eclipse. The requirement to enter an Eclipse of either school would be ONE spell cast of a filler/builder ability. Not 2 like it is now.
To activate Eclipse, you would cast ONE spell from the school of magic you want to enter Eclipse into. For example, casting 1 Wrath would activate Solar Eclipse. (Yes, you read that right. Casting a Solar spell i.e. Wrath, you will enter a Solar Eclipse.) Once activated, Solar Eclipse would last indefinitely. If you wanted to switch to Lunar Eclipse, you would cast 1 Starfire (and thusly enter a Lunar Eclipse), and the Lunar Eclipse would then last indefinitely as well.
This way, you could switch between Eclipses freely without being constrained by the current 15-second time limit. This could eliminate the frustration of dealing with such short windows to do basically everything inside of. Ideally, the Eclipses would remain active out of combat and when entering into combat in an effort to retain fluidity.