Hroka is a great model. She's not an auto-include for me, but I take her if I need a good scrapper, and her power attacks are beast.
Zephyri bonuses are actually great, in my opinion. Brave and Blood Brothers are pretty powerful when used correctly. Ambush is good against exhausted models, but that's about it, but if you can ambush and push into a friendly model, holy shit you're golden.
The Morituri have what I think are the best benefits in the game. Just being able to clear exhaustion on a clear turn is amazing by itself. When you include beasts, holy shit. Add to that the ability to pull off a bunch of effects that your opponent can't react to...damn.
Legio benefits don't seem like a lot, but they're game-changing. They actually result in allowing the Legio to be pretty solid throughout without a lot of drawbacks. Their stats are great, both damage and defense, and they can get out of danger more easily than most others. However, they are prone to bing pushed (only Gaius has a base larger than 30mm), and their vitality tends to be on the lower side.
Magnus benefits are damn good for that favor recycling, they do, allowing you to get more successes. However, their clear turns tend to be lackluster. Rouse. Woooooo.
Also adding to Leika being a spider - in nature, when a male spider comes up and tries to woo a female, there's a significant chance she'll just eat him.