For me the hardest fights are Brynlod and also Magran's Faithful. Dragons are quite easy because you can charm or prone or paralyze them easily with a party and the ads are not that powerful but just annoying.
The bounties however have a lot of high level casters that can really smash you in seconds if you're sloppy (especially if you choose upscaled content). The druids of Magran's Faithful will shower your casters with Sunbeams like there's no tomorrow and so on. Still not supertough if you're lvl 16 or so, but harder than the bog dragons + Llengrath in my opinion.
But yes: the more you advance the easier it gets. Especially with a lot of casters there are no real challenging fights later in the game. The trash mobs you can easily dispatch with your Spell Masteries and in tough fights you can just use all your spells.
Try a party without casters (wizard, druid, priest, cipher). That's a bigger challenge. Not necessarily when fighting dragons, but when meeting big groups of high level enemies (Torn Bannermen, Abbey monks, bounties).
Edited by Boeroer, 16 July 2017 - 01:13 AM.