Here's my two cents about this topic;
All melee sucks unless max'd def. Pretty much pointless to play, you die way too fast. HOWEVER, once you get that initial max def, sweet baby jesus does it feel broken.
As a lower pet user, stick to Paladin, it's simple to play, nothing too hard about it. No skill shots involved, dmg boost and life regen (wew nice!) but it's also the squishiest of the three.
Once you hit ~30hp heals from your pet, I prefer either a warrior or knight. Why? Their kit is so much better. 75VIT makes it perfectly fine without needing that pesky Pally buff to feel like you don't die too fast.
Goofing around? Wanna just not die and still be op af? Roll a Knight. Why? Hella tanky, with nice dps. Though, having a stronger MP healing pet is required for a knight, unless you want to spam pots all day. Being able to solo anything without much hassle is easy. It's my go-to class to farm and max characters quickly. First knight i ever played got it to 2.5k fame. I couldn't die. Then I was careless and rushed a Skull Shrine with avatar underneath it (was stealth and couldn't see it) Made another one, and I get ~20-30 life per day with it. Super simple, super easy.
Though, Warrior is also like this. Faster, but a less tanky. You can kill things with ease. Abyss mobs most of the time die in 1-hit from your attacks. Fairly nice. I never rush things, so I can't help you about that, I always quick clear. Yeah, takes me a little longer, but I don't die. You see most people complaining about dying a lot, but quick clear is the safest way to ensure you don't die and you get loot, which is what this game is about. Profit, profit, profit!
Paladins used to be fun to me. Suuu told me to play paladin after only playing necro forever, fell in love with the char. Feeling super strong, seeing those 400+ hits all the time is nice, but was super squishy. Had to take things slow, but still managed, was fun while it lasted, but wasn't my forte in the end, could be yours though!
You see other players running around rushing things, and yeah, it's nice to be that good, but I am still new to this game, and prefer to just play-it-safe, so I don't have to rebuild a char and waste a whole day to re-Max a character.
So, in my perspective, I like Warriors and Knights more, but you should just find a class that suits you. It's all about YOUR play style.
If you want to farm glands (also effective, gained 15-20 life a day doing this, no dungeons, with a sorc, archer, necro AND wizard). So it's all about perspective. Do what you want with the game, you don't have to dungeon, it's just a simpler way to get pots and chance for UT's/feed.
TL;DR -- Paladins are fun, but squishy. Warriors are semi-tanky, fast, and strong. Knights are tanky and safe to play, could get boring, but easiest to farm with. Glands can also be profitable just stick to a fun class you can just grind on. Best of luck!
