"What situation are you using a card in that both x10 has a major impact on the play and that a break wouldn’t be a disaster?" Just said it, early game and late game.
Early game, where you have a glass card and you don't have a primary suit, use it on a low rank for a low two pair, full house, a straight, a flush. An extra 10 can push you to win in ante 1-3 and a little blind of 4. You win the round.
If Card breaks, removes that particular suit as your primary. If card takes awhile to break and glass card is in the primary, see late game strategy.
Late game. You have mostly one suit, but you have some 2s in the primary you want to get rid of. Can't use any tarot expect Justice. Use it on low suit, or undesirable suit. It's a win-win.
I agree that reliability is important, but I would say making a not useful card have the option to be both great and yeeting itself out isn't a bad strategy. Early game, you won't really know what you are going to do anyway. So, forcing a strategy to come out is pretty good. And you talk about a 3% efficency. That 3% will be with you for the entire game. And if you get rid of more, or change ranks, that 3% really adds up into late game.
And in Late game, you already have a solid idea as to what sequences you are going to play, so an extra bonus(enhancing/killing) is good.
True, glass isn't going to be your B&B, but having a game where you have only reliablity options, with no cards to manage risk is... really boring.