It's exceedingly clear that bosses are designed that way as a staple of the series. It isn't hard to think "let's have a boss that you have to chase through a labyrinth." Or "what if the boss ran around the arena quickly, like a Captain." The bosses aren't designed that way on purpose. They are made specifically to compliment the raid puzzle mechanics and set ups that Destiny has become known for. I'm not saying a boss that moves a whole lot is a bad thing, I'd enjoy it just like anyone else, but it isn't what they do in Destiny. It'd be like having a boss in Sekiro that follows the same mechanics as the Suro Chi fight, or having Oryx running around like he's Captain Quark. There is a specific way they design their encounters, and the weapons and abilities were too powerful for that design.