I'm going to comment on Solrock and Lunatone for now and let other people discuss Beartic. I think the two of them would benefit significantly more with their buffs, and they would probably lead to a healthier metagame, whereas Beartic would just a be really cool offensive Pokemon (and yet another Pokemon to prepare for against rain teams).
As it stands, Solrock and Lunatone have niches of being the only Pokemon in NU with resistances to both Normal- and Flying-type attacks without being weak to Ground-type attacks, outside of the rare and very niche Bronzor. They also have reliable recovery, which means that they can't always be worn down throughout the match. This makes the duo viable enough to see use on serious teams, but despite these great advantages, they don't have the best bulk and thus rely a lot of their typing to allow them to check things. They are also weak to Dark-type attacks, which means that they can be Pursuit-trapped in order for one of the Pokemon they check to sweep later on. They are also weak to U-turn (
DTC you forgot a type), which makes it even easier for them to be trapped when trying to check Swellow.
With Eviolite, however, Lunatone and Solrock would likely see a pretty significant increase in usage—assuming, of course, that their evolved forms aren't also NU and ultimately superior. I don't think that Kangaskhan and Tauros would really decrease much in either usage or viability; they are both primarily used to check offensive teams, so it's a given that a team with Kangaskhan or Tauros will likely have a couple of answers for Solrock. Jynx and Charizard would probably both do fine as well. As with any Jynx check, Lunatone can be put to sleep, putting a lot of pressure on the opposing team when trying to check it. It would also be really vulnerable to Scarf Jynx's Trick, not only losing out on the ability to switch up moves, but also giving up its Eviolite to be Tricked to something else later on. Charizard would be incredibly pressured against Lunatone, 4HKOing it at best with Life Orb Hidden Power Grass and only potentially only 5HKOing it with Life Orb Focus Blast. I do still think that Charizard would be used a lot in spite of this, but it would give stall teams and bulky teams a good answer to both of these huge threats.
Lunatone would be hands-down better in my opinion. While Solrock has a better movepool (with Will-O-Wisp and a Rock STAB outside of Hidden Power Rock), there are more Pokemon that can be used to check Normal- and Flying-types that are already really good. Solrock has to compete with Regirock, Metang, Carracosta, and more to fill its teamslot. However, there aren't many Pokemon that can check Jynx and Charizard reliably, and the few that do handle them are pretty mediocre. Eviolite Lunatone's niche is pretty much unfilled right now, and it would be a really good Pokemon.
