Sandboxing this stuff is kinda pointless. Yeah ok I can sandbox a pillar kiting an obsidian and killing it. Does that make obsidian garbage? No.
Pillar has far more in game utility than Rhino, I explained above why. You get it out quicker, you get it out in more areas, and you are not punished by OC anywhere near as hard. Mongoose + Shields are just the absolutely dominant unit mix against anything before T3 assuming proper apm and kite space.
If rhinos are kiting your pillars, then why didn't you make mongoose. Obviously the map has room for kiting, so abuse the range bot for free kills against the faction with no shields.