To get anything other than unfounded opinion we need to back up everything with stats.
- Code:
<causative> !lg tenpercenters recent /won s=class o=%
<Sequell> 2883/11222 games for tenpercenters (recent): 243/678x Wanderer [35.84%], 239/739x Berserker [32.34%], 75/240x Assassin [31.25%], 115/376x Hunter [30.59%], 99/324x Artificer [30.56%], 507/1703x Fighter [29.77%], 99/342x Earth Elementalist [28.95%], 138/489x Gladiator [28.22%], 91/339x Skald [26.84%], 109/408x Fire Elementalist [26.72%], 81/315x Wizard [25.71%], 75/292x Conjurer [25.68%], 82/330x
<Sequell> Arcane Marksman [24.85%], 123/512x Monk [24.02%], 82/346x Abyssal Knight [23.70%], 69/305x Warper [22.62%], 95/422x Necromancer [22.51%], 73/340x Air Elementalist [21.47%], 68/329x Venom Mage [20.67%], 82/403x Ice Elementalist [20.35%], 84/427x Summoner [19.67%], 90/470x Enchanter [19.15%], 73/423x Chaos Knight [17.26%], 91/670x Transmuter [13.58%]
There is also
viewtopic.php?t=15936 where I analyzed how likely different classes are to break or continue streaks. The advantage of that analysis is that if a player is on a long streak, he's going to be trying harder to win. That makes whether or not he wins a better indicator of how objectively hard it was to win (for a player of his skill level), helping to filter out speedrunners or careless play. The chart of my conclusions is:
In my opinion:
Hard classes: CK, Transmuter, Arcane Marksman, Summoner, Warper, Skald, Wizard, Venom Mage.
Easy classes: Berserker, Artificer, Assassin
Wanderer is consistently one of the highest winrate classes, but I can't find a reason for it to be an "easy class" - I think it's more likely that players are just more careful with it. There is also self-selection bias, because players who are willing to play Wanderer, especially while streaking, are more confident in their skills.
Justifications for hard classes:
CK - no explanation needed.
Transmuter - poor damage starting out due to skills and stats split between magic and might. Worse than Monk.
Arcane Marskman - poor damage starting out due to split skills and stats. Worse than Hunter. Also faces the difficulty that they may run out of ammo.
Summoner - ranks low in my chart, and ranks low in the tenpercenter query too. I know it's not a popular opinion that summoners are weak, but there are reasons to explain why they might rank low in the stats. Dedicated summoners are fragile mages, but they don't have spells that say "get rid of that deadly threat in two turns" like a blaster does. Summoning encourages a character to fight in the open so their summons can get surface area on the enemy, which is itself dangerous. The summons act as a shield in some circumstances, but many monsters will ignore the summons and go straight for the mage, with smiting, lightning bolt, other bolt spells, Portal Projectile, fast movement, etc. Also, summoning is an unusual playstyle, and therefore unfamiliar, which causes players to make more mistakes.
Warper, Skald - poor damage starting out due to split skills and stats. Their magic does not compensate for this until later in the game.
Wizard, Venom Mage - starting book lacks a solid all purpose damage spell of Lair tier. VM also has nothing against early dungeon undead.
Justifications for easy classes:
Berserker - no explanation needed
Artificer - consistently high in the stats. It's not hard to see why. They start with wands that can take care of any dangerous early threat. Aside from that they're just a gimped fighter background, they can pick up any decent weapon and have no problem.
Assassin - ranks high in both queries.
I find it hard to name any more classes as "easy." There is a lot of variation between my chart and the tenpercenter query on most of these classes. I might say AK, FE, Cj, IE, Fi, Gl are relatively easy. These classes are fairly straightforward to play, you can just train your starting skills and end up with a strong character. However, it doesn't seem to clearly show up in the win rates.