It was designed with several purposes in mind:
1. An accurate mid-ranged unit. To deal with roaches, ticks, etc which utterly demolish shieldbots because they have nothing that can effectively take them out at range. The AoE from these units utterly demolishes the generally light, spammy shieldbots, and penetrate thugs shields, rendering half their HP useless. It also helps more generally to flesh out the ranged capacity of the factory (helps vs gunships, planes etc too).
2. A unit beyond 350 cost in the shieldbot factory. Their lack of heavy units suffers late game as such large clusters of light units get bogged up and are easily dispatched with AoE.
4. A genuinely unique unit which interacts dynamically in a new and unexplored way using physical properties, giving tradeoffs and offering synergies with other units. Balancing offense vs defense, having a burst that can be shot at multiple targets, and being charged up by other shield units adds something totally new, and allows a player fielding a lot of shield power to use that power offensively rather than being stuck behind their shield wall.
4. More options in a factory which has markedly less strategic diversity than cloakbot.
What i dont like about it is that its not really any harder to take out than the other shieldbots late game (in many ways, its easier with snipers, penes, bombers, etc), and just how easy it is to drain or waste by tremoring/racketeering/hammering his shield generator or spamming razors kiss/clogger to waste shots.
The major problem is just how hard to use and hardcounter it is. It is a lot like the capcar or roach- utterly overpowered and ridiculous when it works, totally useless when it doesnt. These kinds of 'toys' are nice, but shieldbot really needs more standard units you can safely field in an army composition.