The whole debate rests on one crux, that simply being player availability. The only reason why Bishops, ArchMages, and several other classes still exist is because they're needed at certain times for certain things.
Let's start explaining this. Essentially, Stereo made a great point about Zakum - at least the majority of all classes in this game have had at least one solo, if not almost all, thus proving it possible to kill a boss like that without the use of another's benefits (fast attacking or buffs, whatever). But is that how we all work? Do people go HT and Zakum by themselves whenever they want because they can? No, they can't, and I speak from experience when I say a solo of that magnitude, especially for my class, takes an extreme amount of time and planning to actually accomplish. Alright, it's not THAT much planning, but I'm telling you right now I don't have 8 hours a day and the mesos to spare to solo the thing twice a day, nor would I want to kill 1/3rd of the day for whatever Zakum groups may be in those time slots on that particular channel.
Summing up that point, you need all the classes you can get for special abilities (again, fast attacking, buffs, etc.), if you want to create a run or even do ANYTHING in this game as efficiently as possible. Oh wait, isn't that how life works? You can't do it all in this world by yourself - you need other people. You can't manage 4 AP classes AND Zakum solos every day; you need to go on maybe one 20 minute run a week, or whatever if it works for you. And to do that 20 minute run you need these other classes.
Okay, so we know that simply to keep playing this game or to do essentially ANYTHING you need the help of other people. Now, we know too that you can have 30 NLs in the Zakum Altar and have a run that lasts 3 minutes. What a great way to work, no? 3 minutes is all you need to play this game every day...what a deal! Oh wait, there are never 30 NLs all in one place at the same time unless it's organized, and even then, having a permanent time for all of them to meet up is bound to create problems for every one of them sooner or later (aka some will be unable to come from time to time). So who do you substitute them with? Heroes, BMs, other classes...oh wait, there aren't any of those available because it's a 12am PST time slot (you see where I'm going with this?)...so what's still available? Those other classes - Bishops, ArchMages, Shadowers, Paladins, etc.
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To sum up that entirely, extremely long post, we've essentially proved why the contemporary Zakum run, HT run, or training party exists as a diverse group of classes rather than 30 melee NLs and/or BMs: player and class availability. You're never going to have, consistently every week at one appointed time, an exact group of people together for something. Life doesn't work that way. So we have tons of other classes from which to choose from, and millions of people who play around the globe. Together that makes a humongous array of options 24/7, none of which are the most optimal or efficient, but all of which are capable of success.
Let's start explaining this. Essentially, Stereo made a great point about Zakum - at least the majority of all classes in this game have had at least one solo, if not almost all, thus proving it possible to kill a boss like that without the use of another's benefits (fast attacking or buffs, whatever). But is that how we all work? Do people go HT and Zakum by themselves whenever they want because they can? No, they can't, and I speak from experience when I say a solo of that magnitude, especially for my class, takes an extreme amount of time and planning to actually accomplish. Alright, it's not THAT much planning, but I'm telling you right now I don't have 8 hours a day and the mesos to spare to solo the thing twice a day, nor would I want to kill 1/3rd of the day for whatever Zakum groups may be in those time slots on that particular channel.
Summing up that point, you need all the classes you can get for special abilities (again, fast attacking, buffs, etc.), if you want to create a run or even do ANYTHING in this game as efficiently as possible. Oh wait, isn't that how life works? You can't do it all in this world by yourself - you need other people. You can't manage 4 AP classes AND Zakum solos every day; you need to go on maybe one 20 minute run a week, or whatever if it works for you. And to do that 20 minute run you need these other classes.
Okay, so we know that simply to keep playing this game or to do essentially ANYTHING you need the help of other people. Now, we know too that you can have 30 NLs in the Zakum Altar and have a run that lasts 3 minutes. What a great way to work, no? 3 minutes is all you need to play this game every day...what a deal! Oh wait, there are never 30 NLs all in one place at the same time unless it's organized, and even then, having a permanent time for all of them to meet up is bound to create problems for every one of them sooner or later (aka some will be unable to come from time to time). So who do you substitute them with? Heroes, BMs, other classes...oh wait, there aren't any of those available because it's a 12am PST time slot (you see where I'm going with this?)...so what's still available? Those other classes - Bishops, ArchMages, Shadowers, Paladins, etc.
****************************************
To sum up that entirely, extremely long post, we've essentially proved why the contemporary Zakum run, HT run, or training party exists as a diverse group of classes rather than 30 melee NLs and/or BMs: player and class availability. You're never going to have, consistently every week at one appointed time, an exact group of people together for something. Life doesn't work that way. So we have tons of other classes from which to choose from, and millions of people who play around the globe. Together that makes a humongous array of options 24/7, none of which are the most optimal or efficient, but all of which are capable of success.