Trying to determine if I should buy the 3* offers so I can level up another 3* completely so I can sell it for maximum 4* shards so I can hopefully dupe a 4* and max it so I can sell for maximum 5* shards so I can stay relevant in the game going forward. Does this sound like a good strategy?

It is the only way I can makes sense of this offer personally (not really). Maybe I'm off my rocker....probably.