Actually it's more consistent when they are separated. You want to inhibit gut MAO-A first, and then consume the DMT when gut MAO-A is inhibited. If you consume the DMT too early or too late, the DMT will be partially or completely inactivated. Harmala/Rue extract in a capsule followed by the DMT 30 minutes to an hour later has always consistently activated Mimosa and Acacia for me, i never have dud experiences and it's been completely consistent and reliable/reproducible. With Harmalas/Rue/Caapi in tea form, it's my understanding that the gut's MAO-A inhibition is shorter in duration compared to the gut's MAO-A inhibition from Harmalas/Rue in capsule form because liquid is more easily and quickly absorbed, so for Harmalas in tea form probably around say 10 to 20 minutes between the Harmalas and the DMT, most likely, but i don't have much experience at all with Harmalas in tea form, i prefer capsules, they get the job done very well.
If you combine them, sometimes it'll work, sometimes it won't. I've read a lot of reports from people who have taken traditional Aya down in the jungle and they only ended up feeling the Caapi effects while others were off their rockers lol. It's pretty common from the looks of it. Could also perhaps be a dosage issue, where you need a good dose of Harmalas/Rue/Caapi to inhibit gut MAO-A strongly before the DMT has a chance to be metabolized out, so it could perhaps be that the duds from combined plants are resulting from not enough Harmalas/Rue/Caapi (gut MAO-A inhibition) rather than the combination itself. Plus it's been said that if you have a dud experience the first time or two, it'll eventually start working, which may have to do with the Harmala reverse tolerance (which makes the Harmalas stronger each time it's consumed, if consumed day after day/regularly) so the Harmala dosage would get stronger, inhibit gut MAO-A more fully and protect the DMT.
But i still say it's better to separate the plants, take a good dosage of Harmalas/Rue/Caapi (or Moclobemide) and then consume the DMT when you know gut MAO-A is fully inhibited. It may take a few tries to figure out how long gut MAO-A remains inhibited for you personally, but capsules are better and longer lasting than teas when it comes to the guts MAO-A inhibition so you'd have more success with Harmalas in capsule form, imo.