You can use /wait 0 (or <wait 0> at the end of a line that does something else) to wait only until the previous command executes.

In this specific use case, though, you could try this:

/equipset ##1 <wait 1>
/ra <t> <wait 0>
/equipset ##2

It'll put a one-second delay between when you decide to shoot and when you actually do, but sadly that is the best that can be done using /equipset. The one-second delay is structural and can't be bypassed or removed.

Per the 2022 Reddit AMA from the dev team:

Q: Can you please remove the 1-second lockout on the /equipset command?

A: Equipment processes are running during that one second, so this would not be possible.
This is also an issue for summoner blood pacts and any mage using Quick Magic in a set; unless a way can be devised to allow macros longer than 7 lines, there just isn't a way to execute these with the delicate timing required to ensure the necessary sets are equipped at the right times.