I would roughly define a 1A defenseman as a Norris-caliber bus driver and I would say it's brutally difficult to win a Cup without a guy like that -- unless, perhaps, you have Crosby & Malkin at center and/or unreal goaltending.
I'm all for being optimistic about our defense and I'm open to the possibility that we already have all the components of a future Cup-winning defense, but at this point it's speculation. Lindstrom hasn't played a single NHL game. McIsaac hasn't played a single NHL game. Cholowski and Hronek have performed pretty well as rookies, but it's early days. If the situation at center looks better at the moment, it's because we have a proven 1C in Larkin and a solid prospect in Veleno and we'll probably be adding a high-end pivot in the upcoming draft.
Realistically, if winning Cups is the goal, the centers we currently have in the system probably won't be enough and the defensemen we currently have in the system probably won't be enough. If I had the choice between adding a powerhouse centerman or a powerhouse defenseman, I'd *probably* go with the centerman and hope that our outstanding center depth cancels out any shortcomings we might have on the blue line. Ideally, we get both the C and the D. Though, even then, we're probably still at least one key piece away from being as good as the 2018-19 Lightning.