We are looking into this right now - sit tight for a Hotfix or two while we smooth it out. They aren't impossible, all creatures appear organically, but that may take quite some time, which in practice here is too long. Expect a change in a near hotfix!
A full list of Heart of Deimos Forum Megathreads available:
-General bug Hunting: https://forums.warframe.com/topic/1215584-heart-of-deimos-bug-hunting-megathread-read-first-post/
-New Player Experience Bug Hunting: https://forums.warframe.com/topic/1215585-new-player-experience-bug-hunting-megathread-read-first-post/
-NPE: Feedback thread: https://forums.warframe.com/topic/1215586-new-player-experience-feedbackmegathread/...
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