Instead of Historical Discussion, let me address Lemmy as to why it is used, how it is used, and what it's weaknesses are.
Useful in Strat? Hell yes it is, I was able to reach you guys easily most times, but you had a shit-load of shields and your men equally had the same amount of Pike users, they just didn't know how to use it. KUTT, obviously, is a culprit for skilled pike users. When you have Xeen, Caita, and I picking up a pike, shit's going to get messy. While Pikes are good for infantry fighting and formations, they are also a good way to get your ass kicked if someone knows how to counter it.
In a solo-battle, or a one-on-one, we're going to lose almost every time unless we A) Switch weapons or B) the Enemy is Incompetent. When you see a Pike user jump, block down. They turn away with a chambered pike ready, block down. As soon as they waste a shot attacking you, you have (what feels like) a solid second to get an attack in and potentially begin stunning them to a horrific death. This is a Pike user's biggest weakness, not being able to throw up a block after an attack is made. If a pike user gets too close, hug them, attack them. We can't do shit even if we manage to pull off a spinstab (most times it hits our teammates).
Pike also has wonky hit boxes, there are times my hit box seems to just fly to the right of my weapon or get stuck on something way sooner than it should. However, what makes the Pike great is it's ability to be in formations, work around shield walls, catch unsuspecting people coming around corners, and more. There are a lot of Chaos members who picked up the Pike whom had little experience with it, and they didn't do that great with it. The Pike itself is a weapon that requires a pretty heavy bit of learning I'd say. It's not like a Maul or a Shielded 1hander or Katana that is very easy to pick up, learn, and do good with. Pike takes practice, and given how nerfed it is, it takes skill to use.