Really now. Quickly compare him to Garcia who is currently in upper mid. Garcia is a bit faster. 4 more spd, but 7 base doesn't double much early on (too lazy to bring up numbers though, my guess is that he's doubling loldiers, knights, and severely weighed down enemies, and Gilliam might actually double loldiers and knights after he gains 1 spd since those enemies like having 0 AS), and with only a 20% spd growth anything he does double he won't do so for long. He's going to rely heavily on Garm (braves won't really count as Gilliam can use them too).
But take a look at the durability difference. The def gap is the same as the spd gap, but the growth disparity is huge. 55 to 25 (and 30 spd for Gilliam to Garcia's 20). In addition, since these units are on the slower end, they will get doubled. But the enemies doubling Gilliam are things like SMs that do pitiful damage to him (watch out for mage knights in lategame though, but they might double Garcia too). Garcia isn't going to be able to shrug off their attacks, especially if they crit him.
Or to make another comparison to another upper mid unit. Eir route Duessel. By the time he joins, Gilliam has better raw stats, and gains levels much faster (like, 20/1 to 20/, and the only way Duessel is even going to compete from ch 15 onwards is if he manages to get his axe rank up for Garm, but that is going to take some time as he's not going to double much (granted, neither will Gilliam) which will hinder his WEXP gain, and Garm is still limited uses. Basically, the only way Duessel could win is if Gilliam was negative utility beforehand.
Or yet another comparison to yet another upper mid unit, Joshua. They're pretty much polar opposites. Joshua has poor durability (though earlygame it's okay) and Gilliam has bad offense. Joshua's offense starts off great but slowly gets worse over the game (his spd becomes overkill as more units start doubling, and his str growth bites him in the ass), while Gilliam's durability is among the best in the game aside from a few shaky earlygame chapters. So why is there a tier gap between the two?
I think Gilliam should move above Garcia.
But take a look at the durability difference. The def gap is the same as the spd gap, but the growth disparity is huge. 55 to 25 (and 30 spd for Gilliam to Garcia's 20). In addition, since these units are on the slower end, they will get doubled. But the enemies doubling Gilliam are things like SMs that do pitiful damage to him (watch out for mage knights in lategame though, but they might double Garcia too). Garcia isn't going to be able to shrug off their attacks, especially if they crit him.
Or to make another comparison to another upper mid unit. Eir route Duessel. By the time he joins, Gilliam has better raw stats, and gains levels much faster (like, 20/1 to 20/, and the only way Duessel is even going to compete from ch 15 onwards is if he manages to get his axe rank up for Garm, but that is going to take some time as he's not going to double much (granted, neither will Gilliam) which will hinder his WEXP gain, and Garm is still limited uses. Basically, the only way Duessel could win is if Gilliam was negative utility beforehand.
Or yet another comparison to yet another upper mid unit, Joshua. They're pretty much polar opposites. Joshua has poor durability (though earlygame it's okay) and Gilliam has bad offense. Joshua's offense starts off great but slowly gets worse over the game (his spd becomes overkill as more units start doubling, and his str growth bites him in the ass), while Gilliam's durability is among the best in the game aside from a few shaky earlygame chapters. So why is there a tier gap between the two?
I think Gilliam should move above Garcia.