These missions are an exercise in futility. These two missions are in single-mission chains, and both require items from the Frozen Fury mission chain to be completed. Problem is, it's literally impossible to complete both of these missions and the Frozen Fury chain. This gets a little convoluted, so bear with me.
1. First off, Skeptical Study: Requires 1 Bag of Earth Shards, 1 Bag of Fire Shards, 1 Bag of Wind Shards, and 1 Bag of Ice Shards. This is exactly the same requirement as the 9th mission from the Frozen Fury Part 1 chain (for both Legion and Exile), and since these items are mission rewards, you cannot obtain them again. There is a way around this if you do both the Legion and Exile Frozen Fury Part 1 chains, but...
2. Trash or Treasure: Requires 1 Elemental Controller, same as mission 10 from Frozen Fury Part 1. You get the Elemental Controller from mission 9 (the one that requires the bags of shards). Turns out, you can get two of this item from the Legion and Exile chains as well. So what's the problem?
The Problem: Let's say you do all 10 FFP1 Exile missions first. You spend your bags of shards getting your Elemental Controller, so those bags of shards are gone forever and you have an EC. Well, if you complete part 1 of FFP2 (which does not have Legion and Exile specific components), there goes the EC too. No problem right? Just complete the rest of the FF missions, no more duplicate items. Now you want to do Skeptical Study and Trash or Treasure. Here's the problem: If you complete mission FFP1 mission 9 and turn in the bags of shards for Skeptical Study, you're suddenly without the means to complete FFP1 mission 10 because the bags of shards are gone forever. If, on the other hand, you complete FFP1 mission 10 without doing Skeptical Study and get the EC for Trash or Treasure, you don't have the bags of shards for Skeptical Study anymore. Conclusion: You can't complete all three of these mission chains, only two of them.
So my question is, why on Earth were these missions added in the first place? Not being able to finish the lone missions is annoying, but imagine if a player completed both of them without knowing better, and then found themselves unable to do the Frozen Fury chain. That doesn't exactly seem fair to them, since they'd assume that all the missions are complete-able. If anyone has justification for why these would be in the game, let me know.
tl;dr Skeptical Study and Trash or Treasure missions are pointless and could potentially lead to an unattainable achievement.