Meg and Brom can indeed not be played together until Part 4.
To Rozalia:
Volug is useless for the whole of part 1 as any kill he gets is a waste.
First, that's a fallacious argument. If Caineghis joined in 1-Prologue and magically teleported around the world so he was available in every single map, and started at Level 40 with all stats capped, then every kill he got would be a "waste" (since he doesn't get better) but he would very, very clearly be the best character in the game by a country mile. A character's worth isn't judged by how fast she is improving, but by how good she already is at any given point in the game.
Second, it's untrue. Every kill he gets nets him 2 strike experience. So does every non-kill, for that matter, so if you prefer having him set up kills on knights for others, he can do that (and since only Micaiah and temps can reliably kill knights, this is useful).
Leonardo and Nolan can break that battle easily without much effort and I don't see Leonardo anywhere near the top.
3-6 and 3-12 are generally regarded as two of the hardest battles in the game. I'm not really sure how Nolan and Leo break 3-6... I assume you are referring to Beastfoe + Crossbow, but that doesn't let them tank, just kill. Volug can do both, while letting someone else have Beastfoe, and surviving is at least as valuable as killing there. Then there's the fact that 3-12 isn't vulnerable to Beastfoe.
To Tide:
Hmm, though it's an irrelevant tangent, could Haar's join turn be a EM vs. NM thing? Pretty sure on NM he shows up at the end of turn... 5? But yeah, who cares.
Even factoring in the early Part 1 maps as only half chapters (like 1-P and 1-1 for example), he's still benefitting the team until 1-6 at the very least. Deploying Edward in some of those maps, he's still actually helping the team out with 1-2 range attacks and even when Zihax comes by since his offense doesn't particularly sink to the point of unusable.
I guess this comes down to "Lucia's performance in 2-2" vs. "Edward's performance in early maps". Ed isn't ever as good as Lucia is in that one map, but he does have a few more maps of semi-competence... I dunno. Ed never feels even above average in any map except 1-P because you get better frontliners (Nolan in 1-1, Sothe in 1-2, Aran in 1-3, etc.) and DB maps feel built to park a frontliner or two in a chokepoint and have everyone else lob things from range 2. Ed's range 2 is pretty weak and you only have so many Wind Edges. I'm not really inclined to give much credit for "below average but hey he isn't taking a spot at least" but this might be a personal quirk, I dunno. If you do give Ed credit for being better than an empty slot in 1-1 through 1-6 (though... only barely in 1-4, that map really emphasises a small number of units) then he could go up a bit.
At this point I am pretty certain we agree on all the performance issues of both characters, but are unsure on how to score them.
just don't find Renning to be ever really worth anything at all since he just comes at a time when you're never likely to deploy him. And compared to say the other end game filler like Stefan, he's just loses out to them too.
Hmm, another approach. Suppose someone liked Renning? They think he's cool and want to use him. How much will they suffer for this, if Renning is indeed bad? (and he's pretty low down the list, so he's kinda bad)
My kneejerk is less than someone who really wants to use Boyd will suffer for that. Boyd is further below average than Renning is for each of their first 5 chapters (hi I have the worst Spd of any non-healer GM, the worst Str of any axe-user, and shoddy defences) and in order for Boyd to ever get better you have to either get lucky or spend resources (kill Exp mainly) on him, and even then the end product isn't really any better than Renning I think (Boyd will have a support built up at endgame, and a Strength lead, but Renning has a horse, a Wyrmslayer, higher chance of snagging an SS weapon, and much better Res). Which leads me to think Renning > Boyd. Granted, Renning could still drop a bit because he is currently above two PCs with one good map and one PC with a few okay maps. Consider this a vote for moving him between Edward and Sanaki.
I find Titania's worth probably starting to slump around the time when the hawks start showing up.
Honestly I think Titania is in full on hax mode during this period, though I suspect this is a difficulty mode difference. Titania is probably your only tier 3 PC at this point (Haar might be too and is at least close behind but Haar is where he is for a reason). Gold Knight Titania has offence that is nothing short of disgusting (lol 25 spd 44 atk) and defence which while not as wall-like as Gatrie or Haar's is still evil because it has no weaknesses at all (no, Horseslayers don't count; I'm referring to her respectable Res/Luck mainly here). Other GMs generally don't promote until late in Part 3 short of favouritism or a Master Crown (and the only one before 3-11 is highly contested).
But otherwise I generally agree, as others promote she definitely starts to fall off (offence keeps up fairly well though) but is never bad. Basically she is a character with a lot of availability who ranges from "pretty good" to "wow" which is actually a pretty good summary of Ike and Haar as well, and while I think those two are better (Ike's bases are just too good, Haar's good stats + flight in a team that badly needs it) the fact that there is a comparison says something. I am not opposed to twiddling her with one or more of the Part 4 badasses as I've said, just speaking up for her in general.
I need to respond to Meeple re Nealuchi later, he deserves to be talked about at least.