Great post @MasterSeedy - I do notice one thing that doesn't present itself in these valuations regarding TB omis.
If I'm running Hoth or Geo, this doesn't apply - but I think it's safe to say that a significant enough portion of players are primarily focusing on RotE that it should be a factor. In RotE, we have relic requirements per phase - so not only do I have to apply the omi to use it, but how many times I get to use it in that event is directly tied to what relic level that toon is, and is the supporting team also at the appropriate relic level.
I'm personally seeing this now with the Finn omicron. I can use that one in phase 1 and it remains a full-auto 2/2 team in the mixed zone. Unfortunately the ideal team to accompany him is all at relic 5 as well - so I'll need to bring 5 characters from 5 to 6 in order to get a second battle out of that team. Then I'll need to bring them from 6 to 7 for a third use and so on.
This is the only situation in the game that I can think of where the omicron is limited not only by the game mode, but relic levels as well. I suppose we see a bit of this in the raids - where higher relics directly corelate to higher scores, thus increasing the impact of the omi - but at least in the raids there is never a situation where the omi is utterly useless. At relic 5, my Finn omi can't give me any more value after day 1 in TB, reducing it's usage to twice a month.
I would think that's got to factor into weighing the cost vs. return on these omis, considering that the cost is actually greater than just omi mats - but also badly needed signal data and relic mats.