Blizard inflict some damage over turn and prevents healing (up to some percentage, I don't think it kills), it greatly limits what your scouts/hunters/rangers can safely do, cold resist allows you to ignore blizzard. Typically, they can go north where there isn't much blizzard and they can retreat to your nearby town anyway, but they can't as easily dive deep in the west, where mammoths are, and where the Great Stag generally hangs out.Never used "cold resist" for example and never subdued animals. What do they do for you?
Seems you already found out how to use subdue animals
Taming Fiacra is probably by far the greatest benefit. She isn't good at taking cities, due to her weakness to archers (she can still take out archers with low cultural defensive bonus), but she can steal workers. I personally don't use her much against the Illians/Doviello, I use her in the wild. With flying, she can hide on peaks, making her your best scout and mostly invincible (able to pick her fights); mobility 1 or 2 helps with it. She can help scouts in toruble (double wolf riders are no match), help repell attacks, help herd animals...
The wolf and bear buildings are nice to build in big freshly conquered city, to lose less population to discontent starving; the wolf ones helping holding on it while the bear one helps with culture pressure/popping. One spider pen is nice, two also if you plan on keeping the Doviello strong, more than that is really minor, but the first spider is always nice. Mammoths camp building ability make them the less situational and more generally useful. The ivory resource is nice, but the production and gold bonus alone makes every mammoth worth hunting.
Now with pairs of wolf riders roaming, I'd expect hunters to have a harder time surviving in the wild, making hunt more difficult and animal subdue and resist cold less valuable. Spiders, wolves and bear can be found nearby and are worth taming, but you might not be able to succesfully hunt a mammoth or make use of resist cold before rangers, though I would still give it a try (combat 3 hunters are still very strong).
In any cases, subdued animals are likely die even to simple frostlings if not escorted, hence I love to let my children of Kylorin with the mark of the Raven be hunters: the skeleton herds the subdued animals while the hunter continues roaming. Spiders are hidden, but I think frostling scouts can see them and if the spider is damage, as is likely, it's an easy kill for them; so if you make a habit of clearing frostling dens (I don't), there might be paths that are safe for spiders. Mammoth are tanky but don't resist cold. If you find a place to heal them up, they might make it on their own, but I would put my money on 2 frostlings or on anything stonger than a frostling if it were to encounter some. Wolves will almost never make it alive, but they also are the less valuable IMO, I often explore with them rather than send them home. Bear are the only generic animal with resist cold and have the most decent surviving chances alone I'd say.
I don't know about medic II. Blitz is available to mounted units, and I think animals too. I don't know about recon unit, but I am sure melee and archery don't have access to it, so no blitz Belenus.
"It's interesting how the former Barb-town attracts all the attention. I didn't take a single fight on that famous "entrance hill" yet."
Yeah, I should have mentionned the entrance hill is only relevant agaisnt barbarians who have been dissuaded to go through the NN forest. Mulcarn and Charadon will come from the west. They have to cross a river though, which means either a combat penality or one more turn for your archers and epona to bombard them (though yeah, you often have neither for the first few attacks).
"I do like that Belenus guy much more now"
Yeah, he is only a tiny bit stronger than Caerbulin and isn't stronger than Epona would be for very long, but that actually makes him all the more expandable, which is a big strength. You can be a little bit more reckless, so he levels up much faster and is used much more often. Worse case scenario, you start levelling up the next hero a bit sooner than you planned to.