I've been playing ret for a little over a year now and have gathered the majority of the faction. my local metas (I moved recently) didn't feature a ton of hordes players, so outside of the odd game I had against a legion/grymkin player or circle player (who swapped to playing mercs), I simply don't feel like I have a ton of information on most of the hordes factions.
so, I guess I'm asking what the general strengths and weaknesses are for each of the hordes factions, being most interested in legion and trolls because I like their models the most, simply because I haven't seen enough of their stuff played compared to playing cygnar and protectorate and a smattering of cryx basically every week since I started playing the game. I've watched various battle reports with them involved but I don't quite get them the way I was able to pick up ret, mostly because just the way my brain works I tend to understand focus better than fury.
Legion is probably best described as a glass cannon faction. They are often very fast and have access to one of the best threat extensions in the game, Slipstream. However, they mostly rely on defense to survive any counter attack and are rather fragile if something manages to hit them. There is an exception to this, which is the Primal Terrors theme, which is currently very popular. Some lists use Thrones of Everblight as durable models.
Trollbloods is the opposite, in that they are often relatively slow, but they are durable and have healing mechanics: all their infantry is Tough and most of their beasts can regenerate themselves. They are quite good at combined arms lists as they have strong beasts and infantry and can mix good melee with decent shooting.