The difference for most classes between best in slot and the free lore upgrade gear is going to be like at most 5-8% damage. Half of the gear each class wants is lore gear anyway. As for "raid ready," that would be roughly item level 220. If you're talking about the next raid, then none of the gear you're getting now will help you because easy mode drops and crafted gear will be higher ilvl for some dumb reason - so if you're not trying to enter and clear Midas before 2.4, don't bother getting any non-glamour gear this patch.

So about Midas and raiding in general - how bad does someone's gear need to be for them to be a carry? Not enough accuracy to hit the boss 100% or not enough HP to live through mechanics. It's REALLY hard to gear incorrectly in this game. Parry is trash, but other than that speed/det/crit all increase your damage. Crit might be better, but in general it's not going to be by enough to make a difference for those who aren't going for world first clears. Unless you're like 400 accuracy over cap I wouldn't worry about it.

One thing I'd say is that if someone has a piece of gear that is lower item level than the stuff available on the market board (any piece of armor under 220 this patch, basically) then they are not trying and will probably be a detriment to the group, even not considering their low gear level. Also, not having materia melded to gear you intend to raid in is just lazy. Doesn't have to be tier Vs. The extra VIT on the right side helps a lot.

Rotation and DPS levels are going to vary by fight and what mechanics you need to do. If you're failing DPS checks as a group then either someone is slacking or your tactics are incorrect. Your gear level dictates how much breathing room you have for this (though at this point you can't get much more for Midas). Some fights are really forgiving DPS-wise, like Ratfinx and the blaster/swindler/whatever fight. Others are pretty easy overall but require high burst phases where an individual or the party need to be performing decently. Examples of that would be the lightning chamber on a7s, the teraflare phase of Bahamut Prime (at first anyway), and maybe like Nael. The last group of fights are the ball busters that are just mean and overtuned like Living Liquid, Manipulator, and (to a lesser extent) Brute Justice. For these, you'll need to be hitting your rotation pretty well while also taking into account the flow of the fight - sometimes it is better to save cooldowns when a burst phase is coming soon.

Party composition is more important for early clears when it's harder just to survive stuff and beat enrage timers. At this point you can safely leave stuff like dragon kick at home. However, those buffs/debuffs will still allow you to do stupid stuff like recovering from a 6 stack a7s.

What I'd suggest is getting your rotation into muscle memory. Change up your hotbar position if it helps you notice your cooldowns more. Grab a parser, go do some content you're completely comfortable on (a primal or something) and just try to max out on that fight completely. Once you're doing your rotation in your sleep, it becomes a lot easier to focus on new mechanics and being in the right position.