These are the most fun to play FFXIV DPS classes voted by our players (based on fun/challenge):
As a MNK with Relic who is about to start clearing Coil soon, I love it. I suggest you stick with playing Monk if you love it. It's easy enough to level multiple jobs where you can switch later. I played MNK in XI for about 6 years and loved to constantly push my limits and challenge myself to see what could be done with the class. Tanking on Monk for low man content (Salvage) was easily my favorite thing in the game. Monk is HARD compared to other DPS in this game to perform well with. But once you understand the finer points of the job, it is worth it.
Possibly the highest DPS out of any class in extended engagements.
DoT moves allow you to deal damage constantly, even when you're not in range.
You can off tank reasonably well on certain mobs and hold your own for a solid minute or so before you get killed. Healers and squishier targets will love you for this when your tank is preoccupied.
Final Heaven is an extremely powerful limit break that makes you very valuable (irreplaceable) for fights like Titan or Coil.
Challenging/rewarding game play. When you play your job well and completely crush it, people will let you know because your skill as a player shows through more on this job than the other DPS roles.
Greased Lightning, Twin Snakes, and Dragon Kick buffs must constantly be up to be doing full damage. Most fights that require a lot of mobility make it near impossible to keep these up, which might make your DPS fall behind easier to play jobs like Bard. Perfect Balance gets around this but only once every 3 minutes or so.
A lot of situational moves. One Ilm Punch is powerful but almost never has any use. Arm of the Destroyer is only useful vs. Spell casters on the 4th, 7th, 10th... etc. attack in your rotation right as a spell completes OR vs. 4+ enemies. Shoulder Tackle only works with specific positioning.
Only ranged moves put you in harms way (Shoulder Tackle) or has a long cool down (Howling Fist) meaning if you can't be up close, you don't do anything.
Challenging gameplay. I hate to rag on my fellow Monks, but a lot of people who play the job just don't understand it. Either they don't position correctly for their moves or they cut corners resulting in either sub optimal rotations or missed auto attacks which can result in a massive loss of DPS. Definitely the hardest DPS class to play well.
All in all though, it's action packed and very definitely worth playing.
I know you don't want to play the same class as your friend but is there really a problem with that? My friend and I group all the time on Monks together. On top of that, you get the friendly competition to see who is better.
Really enjoying Black Mage. DPS is something that I've never played as a main in MMOs, and I love magic users. The rotation is easy, and I think it's a great class to ease someone into the DPS role before moving on to more complicated rotations from other classes. There are still some neat tricks to learn as a BLM outside of the rotation though. Currently working on WHM and PLD, really looking forward to tanking.
I once had a level 50 culinarian in our group. He used the level 3 LB and proceeded to bake all of our enemies in a giant oven. Needless to say, we ended up getting monster cookies as a reward from those mobs.
Arcanist is by far my favorite. I'm a SMN most of times unless fellow FC or the like need a Healer, in which case I switch to SCH. SMN to me is so versatile.
You can Tank, though not even remotely as effective as an actual tank, really helps soloing though.
You can spot heal when needed. You can really save a party with that especially with Resurrection.
You can DPS multiple enemies at the same time with Bane, though not significantly as a regular DPS.
You have a Summon that deals damage for you as well as your usual rotation and some nice Cross Class Abilities. I just put my attributes equally into both. That practice may be frowned upon but it's not a game-breaking difference anyway and I'd rather be multi-purpose as that's the style of ACN anyway.