The Alpha Slot is effectively an enhancement that applies to all powers. The baseline enhancement (“common”) is one of four types (accuracy, damage, endurance, recharge), and improvements add other enhancements like healing, stun, defense buff, etc. Depending on your character, these higher-tier improvements may be more important than the baseline choice.
The first good design decision is the ease of creating a common Alpha enhancement. Complete a short story arc with one difficult mission to unlock the slot. Run a level 50 task force, and you will be at least 2/3 of the way to filling it. Everything level 50+ can drop Incarnate Shards, so even a solo player running missions has a chance to participate (slowly). This is the first step, everyone gets to play, and rewards encourage grouping.
By the City of Heroes drop system, every enemy makes the loot roll for every character. It is theoretically possible for one minion to drop an Incarnate Shard for everyone on a team. The odds of that on a full team are estimated at 1 in 1,000,000,000,000,000,000,000,000, so probably not, but it will happen with elite bosses or archvillains occasionally. No competition for loot rolls, and you do not even need to tell your teammates when you get one.
Another aspect I like is that, as City of Heroes typically does, these are character unlocks not inventory items. You
currently have four common and eight uncommon Alpha Slot options, soon to expand with sixteen rare and eight very rare. [Update: 19.5 is live.] When you build one, your character has it, done. If you decide to switch from yellow to blue, your character can switch back to yellow later with a few clicks. It is like swapping talent trees with pre-built options. If you want to build all eight very rare options, go for it you insane completist. (There is the wrinkle that building an uncommon consumes the common you made along the way, but the only reason you would want that common back is because you are building the other uncommon. If you are a truly insane completist, you can build all eight very rares, then backfill the sixteen rares, then…)
The design problem is the clunky City of Heroes inventory system, most of which was jury-rigged after launch. Incarnate Shards are yet another variety of salvage, so it uses that window, but filling your Alpha Slot is a separate window accessed through the power window, not the crafting or enhancement window. The Incarnate power window itself has elegant tabs, but it is hidden behind that power window. If that is documented in-game, I missed it, spotting the right button while doing something else. It could also be more visible in-game how to get the Incarnate components other than combining shards.
Update note: we have in-game reports that using one of the new rare Alpha Slot options will cause random crashes (pets’ powers not updating to the level shift?). Updates may appear in the comments.