Something I noticed about Ast cards on summoners...

[NessaWyvern]

When you use astro cards on a summoner, the card spreads to the pet but.. When you use time dilation on the summoner, the pet doesn't get the effect of the time dilation, their card wears off sooner than the summoner's card.

Does this mean that its better to use time dilation on other classes, than on summoners? Their pets wouldn't benefit from time dilated balances, arrows and spears.

[HyoMinPark]

I’m guessing it would probably depend on where the SMN was in their rotation: if the card is going to miss an Enkindle or a Bahamut window, it would probably be better to hold said card until the SMN was actually in that window. But if they’re in a DWT window with no upcoming Enkindle, it probably wouldn’t be too large of a loss for the card to fall off of the pet before the SMN.

[Mansion]

I mained SMN up until 4.4 and switched to AST since then, but I think SMN (and MCH) are the most tricky DPS to give individual cards to; because of that burst phase that you need to identify to gain full potency.
From what I understood, now SMN play Garuda and align their Contagion on the Ninja trick attack (every minute), so giving them a card roughly before/during that phase will be highly beneficial. I would not worry that much about pet and time dilatation on SMN as their burst phase is 20 seconds for bahamut and 16 seconds for DWT, and are sometimes followed by a "downtime", so a standard card duration would be enough I'd assume. Feel free to correct me if I'm wrong
I'd rather keep time dilation for a spear on a BRD or MNK, or any DPS with a more consistent damage output.