All cards have uses, some just more niche than others.

Balance, Arrow and Spear are pretty much self explanatory.

As for Ewer, Spire and Bole, I'd rather have these cards for Royal Road than having a button that makes the DPS increase cards AoE or extends their duration, as it's more interesting to me that way, but also because they do have other uses:

Ewer: Can toss it on someone else or yourself after being resurrected to get some mana back, and can also work to increase BLM DPS, potentially giving them an extra Fire IV, or on yourself for more Gravity.

Spire: Same as above but on TP using classes, could also be used to allow a DPS to keep using TP heavy AoE skills such as a DRG, which is a DPS increase. (But pretty much only in dungeons.)

Bole: Good for progression when you are testing the waters, excellent in dungeons as it allows you to cast Gravity more often.