So after playing quite a few games of SC2, I've been thinking about the use of Tier 1 units in the end game. Most Tier 1 units have their uses, and even the late game scene can be used to counter certain units and combos. Marines are still used as a backbone, zerglings are great immortal/stalker counters, even banelings can be used to destroy large late-game infantry forces.
One unit seems to lack use in the late game scene in my mind, and that's the Reaper. While this unit is great for countering light units, fast for raiding and has great building damage potential, I can't see this unit getting a lot of great use in the late game. At a cost of 50m/50g, this unit is simply too gas heavy in the late game to be made as a proper counter.
I think units like Hellions are much better used as light counters, due to their splash damage and no gas cost; as well as the fact they can be double pumped from one factory with a reactor for situations that necessitate anti-light units. Even a decent mass marine/marauder force can handle most light units. Reapers are great early game zealot killers when you have time to micro; but if we're talking about late-game mixed forces and speed upgrades, the Reapers take a backseat and are killed very easily.
I sort of think the Reaper needs its gas cost to be lowered, and perhaps allow it to be made though Reactors after a certain point. To prevent early game rushes, have their cliff jumping be a gas-heavy researched ability to prevent early harass. The cheaper cost and easier production might give it more of a late-game purpose to be made.