Yeah i myself separate the DMT and Harmalas, i wait 30 minutes in between usually, it's always been consistent and reliable. However, i've read a lot of disappointing results from people who have taken both at the same time rather than separating them. Some seem to do fine when they're combined, but separation seems to be the best way to go. With Harmalas/Rue in tea form, the duration of gut MAO-A inhibition seems shorter compared to that of Harmalas/Rue in capsule form, so in tea form i probably wouldn't wait anymore than say 10 to 20 minutes, whereas with capsules 30 minutes to an hour seems to do fine, less or more than that and the DMT may have trouble being activated, as you want full gut MAO-A inhibition so that all of the DMT is active. Though if you consume the Harmalas enough regularly, a reverse tolerance will start to build up, and the Harmalas will bind tighter to the MAO-A enzyme which will inhibit it faster, better, stronger, which helps when it comes to all in one teas (Harmalas and DMT combined).
But you don't know how many times i've read from people on the Aya fb group that they didn't have much in the way of effects, or they didn't get effects until about their 3rd time or so, and people wanna keep coming up with dumb excuses like "well maybe you were blocked up" or "the medicine was still working even though you didn't get much out of it" or "you need to do such and such diet and then Aya will work". They come up with excuses as to why it didn't work for someone rather than telling them the truth that it's because DMT wasn't active. Harmalas have no issue being active and are fine given that you take a good dose, but because of DMT's activation issue, it may or may not work, so it's better to inhibit MAO-A first and then consume the DMT. You don't hear/read of people taking Psilohuasca or other Psychedelics and the Psychedelics not working, because the rest of them are already orally active and will no doubt work, so it's obvious the reason why Aya or Pharma doesn't work for someone is because DMT isn't being properly orally activated.
I personally would vote for separation of the two compounds rather than combining them, even if i didn't have any issues with DMT's oral activation when they're combined, you just get a lot more consistency out of the separation of them.