First time I've seen Rain bundled? ITAD also doesn't note any other bundles for it

Conversely, if I've done the math right, Stellaris Galaxy Edition could potentially count as bundled (by SG considerations)- after calculating the fact that the expansion has gone 81% off and the base game was BTA, it seems to be in a somewhat iffy price range (though even if it manages the numbers, it's only really a consideration for bundle listing if anyone on SG ever actually took advantage of that circumstance).

[The main point there is to emphasize that the T3 is underwhelming, if that's not clear.]

So ultimately, it's still potentially just a single unbundled inclusion either way, if we're going by SG considerations.
(On the other hand, if we're going by non-SG considerations, I think Starpoint Gemini Warlords would still count as unbundled.)

T2 isn't any better- Humble split up the Galactic Civilizations 3 components as seperate listings, even though the store page curently offers all of those as the base singular purchase. Whoops.

I don't recall Stellaris ever having low overall reviews, at any point. It was rather well received at the start, as far as I recall, rather. According to my friends that play it from the start, the devs did change a lot of the foundational design elements along the way, in a way that most of my friends didn't care for. But even if that's not just subjective preference, the game does still seem to be very well considered despite that. More notable is the DLC/expansion spam, and the fact that so much of the game is based in them.

So, in short, it should be a good game, even now, but the concerns are with foundational systems changing randomly and with the large amount of dlcs/expansions out there. If you're already hesitant on it, getting it at T3 (especially when it was already at T2) is probably not the ideal approach, given the liklihood of not only getting it cheaper, but of eventually seeing it bundled with some DLCs.

Also, as I noted in a post above, the G3 "DLCs" seem to now be considered part of the base game, so that's something to keep in mind.