They are horrendous--another poorly thought out part of the poor end game. Frankly, they feel like an afterthought.

IIRC, the second tier opens up at skill level 65. The range on the mission selector refers to the character level of the items or mats you'll receive.

It certainly makes a good badge of how little one does other than play SWTOR.

Some you can, but I have some stuck in my log which require entry into instanced areas that i can no longer enter because I completed the main quest.

All of them can be used effectively, depending on your spec. Tharan will generally give you the least downtime between pulls though.

You actually don't need to complete all side quests and bonuses to keep up to level with your class quests. Not even close, actually, especially if you do FPs, Heroics, Space battles, or PvP. That being said, more content is always good. It is also expensive to develop and I'd much prefer that time and money be spent on endgame content at this point.

Companions cannot equip class-restricted items.

When I first hit 50, I used planet commendations (of which I had many saved) and ran low level FPs solo to get orange moddable items and then crafted the appropriate mods.

Tier 1 scavenging missions or buy it from the Crew Skills Vendor.

You have (or will have) a companion who loves cultural artifacts and two that like rep memorabilia.

I consider this a FAR FAR better alternative than having the quest gaps that other games often launch with.

Generally, I agree. While leveling, I rarely go for a purple schematic unless it is a slot I will be using for quite a while.

I bet you won't. In thousands of items, I have never seen a crit on any enhancement, mod, barrel, hilt, color crystal, grenade, etc. I have only seen crits on fixed-stat slot items such as (non-orange) armor or weapons.

What is the difference between watching your companion's progress bar or your own progress bar other than with the latter, you can still do other stuff too?

WoW invented quests? It would have been funnier if you had blamed EverQUEST.