In the first part, you're asking that rare drops be made useful so that people will feel some compulsion to farm it, and, in the second, you're saying that they shouldn't be required or BiS even though, unless the gear actually *is* BiS, you're never going to see people farm it or care about it all that much (excepting it being several tiers of better quality than what the normal drops are, such that it's only *slightly* worse than the actual BiS).
Take this example:
LI HM Rare Drop: Implant of Power - 20 Endurance, 280 Power
Kaon HM Rare Drop: Implant of Devastation - 20 Endurance, 200 Crit, 80 Surge
False Emp HM Rare Drop: Implant of Willpower - 20 Endurance, 280 Willpower
D7 HM Rare Drop: Implant of Surviving - 100 Endurance, -5% Inc Damage, 100 Power
Each of these implants *could* be best in slot, depending on the rest of your gear. If you go for the LI implant, it means you need to get your crit elsewhere. Go for the survivability implant and you'll need damage from elsewhere. The point is, each one is useful, they are comparable incomparables. Each one offers a boost to one area of stats at the expense of another. Its all about choice
Tbh, I don't expect it to ever get implemented as it is extremely hard to balance out, but I've seen it done before in LOTRO and LOTRO's itemisation (with the exception of radience) has always been miles better than in TOR imo.