Right now I'm about level 55 (80 being the level cap). I play a Herald of Xolti. Think a berserk Viking wearing underwear and a two handed axe and you've got a pretty good idea what a HoX does. They are considered in the mage class, but really don't have any offensive spells. Almost all of our damage comes in bursts through the combo system; a repeated series of keystrokes to perform a move, similar to Street Fighter or Mortal Kombat.
Gameplay: Being a HoX means that you're probably looking to sologrind most of your levels. Seems everytime I try to get into a group they say that they have a Ranger or an Assassin already and don't need any other DPS classes. Which is ok. You can do about 90% of the game soloing quests and the rare occasional level grind. Quest items are rarely geared towards HoX's. Usually your destiny quests will yield items for your HoX. Green items (good quality) are pretty much going to be your norm for gear. The good news is that HoX gear is cheap on the AH.
Crafting: Some bugs still need to be worked out, but I chose Weaponsmithing/Gem Crafting. One of the nice things about those two professions is that I can slot my own cut gems into the weapons I make. I made a 2-handed Blue two-handed sword when I turned 50 and slotted it with three gems. I recently did a quest line where there was a really good 2 handed Axe (Blue/superior quality). I used it for doing a daily quest and found myself not killing the mobs as quickly. Even though the Axe had about 5 more DPS than my sword. I'll probably be using the sword til I ding 60 and can then start crafting my T3 weapons.
PvP: I have no experience PvPing as of now, but will probably be looking at it around 70, just to get my feet wet.
Conclusion: I can only comment from this point of view. Others may have differing opinions. But I really like playing my HoX. Nothing more satisfying than taking a lot of damage, then ripping someone's heart out, gaining back about a third of your health, and beat the everliving snot out of that mob. Fatalities are nice. I have one that I stick my weapon into their chest, do a little laugh and pull the sword out. Another one I burst a guy into flames just by looking at him. But the best one is the one that I'm cutting the mobs head and two arms in a couple of sword strokes. Fatalities = very quick stamina boost, which is nice because I use a lot of it for my combos. It is a unique class to play. Don't be looking for this class to be the OMGOVERPOWERED class in the game. But if you like a challenge and hate the smell of leather in swamps, then I would recommend the Herald of Xolti class.