The work is what makes her the best. She overpowered Innes when you max her and put them side by side, and Colm's support, like you said, made her amazing as a sniper.
You can raise units that will be better than her without all of the work. Innes is not that good either, so being better than that isn't saying much. You want good 2-range? Just use one of the really good Paladins with a Javelin/Spear.
lol Seth is this best, but he's an EXP taker. He takes whatever EXP you were gonna use on the grinding for the little ones. I'm sure he was buff'd that way because at the beginning it's difficult with just a lvl 1 lord and him. Next chapter you get like 2 people, yea, but they still blow. He was like a tank.
Umm, what? Franz is the best Cavalier you get. He'll have great Str and Spd for doubling, decent Def and great HP for durability... And you get him early on and he's around all the time. He's the exact opposite of blowing.
The lockpick wears off fast and because of the numerous chests and doors, so I leave Colm to being a Rogue. He has HIGH evasion, so even at higher levels he can put some damage while avoiding pretty much anything. I made Joshua an Assassin because you pick up Marisa later and she's my Swordmaster. That and when you're playing the 'extra' part of the game, you unlock Joshua's mom, Queen Ismaire, and she's a Swordmaster, too. You don't need 3 Swordmasters, and one Assassin is plenty. I wish you could get 2 Rogues in the damn game and the 1 Assassin, but it's either or.
You can get about 4-5 Lockpicks before Colm even promotes (a couple more after he promotes, but he won't be able to steal one of them). This doesn't even include the Secret Shop. There are not more than maybe 50-60 chests in the game not including the tower, and how often do you need to open doors with the Lockpick rather than the 2014901950 Door Keys you get? Your Paladins will reach doors before Colm will especially if he's going another route to get treasure, so they should open doors later on. I've been through this game several times and still had a couple of Lockpicks left for post-game.
And you can get 2 Rogues in Colm and Rennac, but Rennac sucks beyond his Rogue abilities soooo... And yeah, you don't need 3 Swordsmasters, that's why you use Joshua and bench the rest. >_>