If you do 10k DPS on your MCH then that 3% is an extra 300 DPS. That is lower impact then throwing the non-optimal card from the old system on you. It also only lasts 15 seconds so you wont even feel it because it effectively has no impact at all. They are useless. It is better to minor arcana it and throw it on a healer or tank of the appropriate range then throw it on the wrong DPS. Cause if your tank is only doing 8k DPS then that 8% Lord of Crowns card boosts their DPS by 640 compared to 400 if it was tossed on your MCH at 10k DPS. Even without Minor Arcana it is better to toss a melee card onto the tank when you have no melee to put it on. If you have a co-healer and only Melee DPS then any ranged card is better tossed on the co-healer.
The reason why a low power boost like the Dancer standard step buff and the old AoE Balance buff were worthwhile was because despite only minorly boosting damage they did so over a long duration. AST could boost the duration so the entire party had 40 seconds of +5% damage and boost the top DPS to have 55 seconds of +5% damage. Dancer buffs themselves and their partner throughout the entire fight as they need to use Standard step on cooldown as an attack as much as a buff. The sheer duration is what makes the buff worthwhile the lower the strength goes.
Now the reason why the old DPS buff cards could be so strong and impactful was because there were utility cards mixed in as well. Which also meant the utility cards could be strong. Sure in optimized 8 man savage raids Bole was seen as useless because they only wanted AoE Balance, though that was not the only content and in all other content Bole was useful for a wide range of reasons. Ewer in optimized 8 man savage raid was not very useful aside from being an AoE burn, but in all the rest of the content it was useful because in 24 man raids or 8 man normal raids deaths were common and in 4 man dungeons gravity spam ate you MP like hell. Spire had the most niche use and was indeed the one mostly useless card, it needed a rework.
Overall yes the new cards are "reliable" in that they are generally useless for the given amount of busy work that you need to do. Their durations are too short for the strength of buff they give. As they lack utility cards to be counterbalanced against they cannot be permitted to be strong, as such they remain feeling impactless. They also made it just as frustrating if not more so, because while there was minor disappointment in not getting the card you wanted previously you are getting handed literally useless cards that feel worse to use if you have the wrong class configuration in the party. It is not amusing when the only person I can buff is the tank because the cards are pointless on every other person in the party.