Jamke

Heavy blade is not a good "A" skill, it's better as a seal so I recommend not to

If she was +atk then yes, otherwise no, unit needs to have a huge atk stat to use heavy blade, thats why majority prefers said skill as seal slot

It's only viable on Cordelia if she's +Atk and is generally run with Firesweep Lance on a flier team, with significant Atk buffs. You would normally run her with Galeforce and Quickened Pulse, for it to proc on her first attack. Otherwise the skill is useless on her.

Build him because he's awesome