Some people might already be aware of this, but I'm gonna put it here anyway just in case any aren't and this helps them plan ahead.

So the meta objective (the one that gives 1 piece for all heroes) will be a random slot. But the smaller per hero objectives will only drop gear for your lowest slot(s).

Example for anyone who hasn't already experienced this with OLT/Raid or past events:

If your 4 main pieces are all 150 PL, you'll get a piece for one of those 4 slots (since they're ALL technically your lowest). Now let's say you complete one objective and get a 152 melee piece. The next objective you complete as that same hero can only give you a piece for one of the other 3 slots, and so on.

So this is something to keep in mind if you're trying to get specific pieces, such as the ranged damage buff pieces.