Pantheon should have a passive indicator same as Annie does with her stun.
"After landing 4 basic attacks or abilities, Pantheon blocks the next incoming basic attack from an enemy champion, large minion, large monster, or the next incoming shot from a turret."
The most annoying thing about fighting pantheon is keeping track of his autos to know when his passive is going to go up.
Since champions like Annie, Jhin, Xayah, Graves, Corki, ETC. all have indicators added to their health bar they have been better to lane against.
I believe that Pantheon should have a passive stack count added under his nameplate.