Shard Requirement To Unlock Related To Character Strength?

Shard requirements in most cases don't determine a character's worth. Only time I'd say it's relevant is for legendary and hero's Journey characters.

it's only important for when you're buying chromiums and bronziums to a lesser extent.
full drops for characters that unlock at 1 star totally suck.

Kinda, sorta, but not really.

Generally speaking, stronger characters and more important characters unlock at higher shard counts. But there are always exceptions (Biggs, First Order Tie Fighter, Deathtrooper, etc).

More importantly, though, no matter how many shards it takes to unlock a character, it always takes the same number to finish a character: You need 330 shards total to hit 7*, whether they unlocked at 1* like the FO Tie Pilot or unlocked at 5* like Grandmaster Yoda. Their power at 7* is ultimately what matters most, and that tends to be more a factor of where you get the character than what level it unlocks at. Powerful characters tend (again--not always, there are exceptions) to be located in the later cantina and light/dark boards, or have fewer slots and be less common to find in rotating stores like Fleet or Guild stores.