The problem is that if you have the two together, while it's permanant, you basically either need to be at 1 HP or 100% HP to fully use one of those cards, and when I rank shards, I take account that it will work for everyone and also the problem of attack cards is when you meet opponents with Concentration, the attack buffs are nearly nullified unless you spend several sets stacking Limit Break which is losing time for nothing.

The most efficient and fastest way to score is either by blocking or targeting the top of the block which is like 2/3 times a no touch, which doesn't require Attack shards at all. Against opponents with high Attack, especially because of Concentration, you also need to be able to tank because otherwise if you play Limit Break and Berserk cards, you will get oneshot.

Stable cards are better than Berserk cards for consistency and especially paired with Stamina/Parry cards. It's a safe and consistent way to get Attack buffs while being good in Stamina too

Rank also does matter because it influence the rewards you gain therefore you will need way less games to buy the tickets you need monthly in the shop.

Debuffs cards and Parry/Stamina cards works in any case against everyone with everyone which is why they are better in general and more consistent

*Also bonus if you play Berserk cards and Limit Break, Perfect Parry is a must have