Usually End of Turn effects trigger in order of the cards played/summoned. The issue I just experienced: Bloated Leech triggered before Magtheridon, Unreleased, despite being summoned after him.
I looked around the internet, but according to the wiki dormant entities do not take a special position in the order of play, so Magtheridon should trigger before the Leech.
I don’t know if it’s a bug with Dormant/End of Turn in general or a bug with Leeches in particular (a Hideous Husk was also present!) or maybe even an intended interaction that has never been documented. Only have the one example I explained above.
EDIT: Next one: Ancient of Yore was played first. Sanguine Infestation afterwards. The triggers were Leech → Ancient → Leech. So it’s completely random. Now it’s just a matter of bug or no bug.