I would prefer Balance. Simply because with Ninja and Bard, our damage goes to 1 * 1.2 Voiced Foe * 1.1 TA * 1.2 from RS * 1.05 from Enochian. That's a total of 1.6632 multiplier. If you have an extended Balance (15%) That card is actually 24.948% for a total of 191.268% damage boost. So a F4 that is usually 504 Potency (260 Potency * 1.8 from Astral Fire III), you have spam nuke spells of 963.99072 Potency.
Right now I can hit for 12k my Fire IV without Astro if I crit. With Balance empowered, I'd be close to 14k per spell.
Spell Speed is nice but I would prefer an extra damage boost from my 20 seconds opener over making it quicker. Also, if you are asked to Balance another job than BLM, he is a complete idiot. BLM has the highest opener burst atm. The closest I saw was Machinist and that's to take account the Machinist didn't provide me Foe and I was still doing more burst. People may argue about this but to me it's obvious a Balance card that isn't on a BLM is a wasted card for a raid DPS parse. This is also why I dislike Astrologian so much; Astrologian mainly buffs 1 person. The buff will be better on your best DPS. If you were in a group with the best DRG in the world and an average BLM, the most logical action would be to give that Balance card to the Dragoon.
Also, I don't think you are derailing the conversation. Astrologian support does include us, BLMs.
Weren't you a Midlander? I can't help it. Needs everything possible to beat A4S x.x