My opinion as someone who is actually progress-raiding and playing ever since the launch of Version 2 this game is too easy.
I'm speaking of battle class-content since this is the most obvious one.
(My boyfriend could probably write an essay about crafting and gathering in 3.0 since apparently crafting and gathering is the real endcontent right now... but yeah.)
Apparently this game is not too easy for the most of the player base, but when you're decently skilled or at least capable of reading the tool tips of your class, you'll probably end up being bored.
The main problem currently is that there are only 2 types of difficulties: babymode and hardcore.
I'll count to babymode: EX (because, let's be honest here, you can be carried through Ravana/Bismarck by now if the other 7 are decently skilled or have enough gear), Alexander Normal (for obvious reasons, you can play this drunk and still not wipe) and dungeons (which simply don't offer any difficulty).
Hardcore: Alexander Savage
But even there exists one major problem: A1 and A2 Savage are ridiculously easy compared to A3 Savage and above.
For example; my static has beaten A1 and A2 with almost zero effort during the first ID when it released, but we're having major problems in A3 Savage ever since then (dps is not much of an issue, but the mechanics as europeans due to server delay are a pain). I mean - how many groups have killed A3 Savage by now? Only merely around 10 - worldwide? No clue. People even say A3 Savage is more difficult than T7 Savage back at IL110 times, but anyway. A3 and A4 Savage are literally the only fights who are ridiculously hard and require a lot of work, even for skilled players. Almost 700 wipes till world first in A3 Savage makes one cringe. In pain.
There is nothing else. Nothing.
And only two bosses for the hardcore is...not a lot.
There is no other challenge than beating A3 and A4 Savage right now - and this is what makes people complain.
I'm not saying this game is overall boring. No.
I still have fun playing this game. If you're bored, you're doing something wrong.
But for someone who is enjoying challenges and who is trying to play their classes perfectly this game isn't offering much, currently.
I'd say the game is complex for newbies and casuals who simply enjoy playing the rpg-elements or the game overall; but for anyone else it's too easy.
I simply refuse to call this game 'difficult' or 'complex' simply because of two bosses which probably won't be beaten by 99,5% of the whole player base.