I don't really get your point
1. It's good that World bosses have the chance of dropping even end game items, those drops are really rare but they make it easier for newbies. The game has changed a lot it terms of progression over the last two years.
Orkham and Grafu are both very high jumps in terms of overall gear and DMG therefore it was very hard for newbies to catch up.
With the new systems introduced (title nerfs,WBs, Newbie Guild ) this issue was already taken seriously and devs give their best to make it easier for newbies to join the game.
It's completely normal that with time items will get easier to obtain than at the start.
Also ofc I don't now total player numbers but for me it feels like since the WB update a lot of new players join and stay again ^~^
About the bard skill, if I remember correctly it can only be used once and has a long CD after and it deals some % DMG to a boss depending on it's current HP. Yes it's a strong skill but it's not even close to be OP especially in the lower content that you mentioned. Since if you geared you can nuke bosses if you are not geared you will deal some DMG with the bard skill but die afterwards since your other skills won't deal.enough DMG .Also if it is about starter region it's not a problem because those bosses are no challenge anyways O.o You can kill them with any class it doesn't make a difference and if you meant WBs it doesn't make a difference there as well since you need a lot of players and even a raid group with 36 players only need a very low amount of overall DMG at the WB to.receive a reward.
And with a geared character the skill gets obsolete anyways since in lower content every class can just nuke bosses at some point with current gear.
Altho you have a point if you meant that the bard skill can be to strong for WBs since right at the start it can deal up to 10% DMG ( maybe giving WBs immunity to that specific skill could be considered if it would influence it but tbh I never saw a situation where that was the case ).
Greetings Miraiyu
Here are some videos of current content and lower content in case you don't believe me the Fakt that it's possible to nuke bosses without bard