To me Shadow Lairs seem like a large portion of content that individuals might only do a few times for gear and just never do them again... I don't know... it just seems like a lot of effort went into a part of this game that people don't really get to experience much and have little replay value.
If there was actually a way to experience Shadow Lairs more without flooding SL gear would people actually want that system more than the current one? I'm not saying they should be spammable like ranked missions but if they could be just a little bit more common such as random tier 3 arcade encounters or perhaps if there would be requirements to access crafting instead of the actual SL entrances...
I have been wondering sort of the same thing for awhile now. I never felt the need to do a SL because the gear is not very appealing to me and the cost of going is quite a bit. I always wondered what would happen if you only used the key after the boss to go the sanctuary and Unknown Passage. Would more people do a shadow lair then? This way if you wanted the gear you could still get it but if not then you can still do a SL (just no SL mat).