But I just did this fight the other day and had such a different experience that I am dumbfounded.
So first, Any character I have on the rafters I keep distance between them and him. I also use grease, ice, etc to keep him away and make him slip. I dont do this because I think the shove here is over represented, I do it because the rafters feel like a high risk high reward area to fight, so i choose to be very tactical and slow about fighting in places where i can get shoved into very bad spots.
Second, I pushed three enemies into the spider pit where they were gobbled up by spiders, and not once did i get shoved.
Third, any character vulnerable to shove (melee for example) i used on the ground to fight enemies. Range played on rafters.
Fourth, Shove is 100% success from an invis enemy - so I use githyanki mage hand which is invis to shove people off. You can also use mage hands between you and enemies with a narrow path so that they have to kill it to get to you.
That sound like a very cool an varied encounter. I do feel it is your creativity shining through rather then result of the game design. Really, getting shoved down is the only dangerous thing that can happen. Line up against the wall, or up the stairs, spend some resources and the battle is won. Enemies are easy to hit so +2 from high ground isn’t that beneficial.
I feel it is where, at least for me, 4 player party might be an issue - with only that many players there isn’t really space for support class. Conjuring mage hand to block a passage seems like a waste of time if I can kill an enemy in the same move, same with casting Crowd control spells. Doing fancy strategies feel like prolonging the fight, rather then fighting smartly.
Of course, there are also the abysmal push arrows, but I am not sure if they are present in that encounter.
Prof. Dr. Dr. Mad S. Tist 
