I think as it is now its pretty stupid. The Endboss should be a reward for clearing the wave and filling the Meter up.
As it is now its pretty retrded. If you dont get the Meter up in the same round the boss spawns in the middle of the fight completly fcking up the wave.
for example starting a fresh 20 wave is pretty easy coming from wave 19 to 20 with a half filled meter and getting unlucky that the minibosses spawn all at the end and on top the endboss spawns its absolutley impossible to clear the wave.
He spawns kinda at the end but not rly if youre not able to fill the Meter up in the same round. If youre able to fill the Meter up at the end sure the boss spawns at the end. At lower waves it doesnt matter but as soon as you get into higher waves it can become sometimes impossible if youre unlucky how and where the minibosses spawn. (sure premade 6man who 100% know what to do might be still able to pull it off but a wave 20 shouldnt be that hard just because youre unlucky in what you get)
I think there should be a consistency at how difficult the waves are. If youre unlucky wave 20 with bad boss spawn is super hard - wave 20 without boss or good boss spawn is a walk in the park.
They already spawn each wave. That is the whole idea of the meter and killstreaks. If the team have the tactic and ability to fill it each wave, they get boss. If they just want to progress without wiping on boss they can do that to depending on tactic and trying not to fill it. Pretty much the whole idea of the instance which ur suggestion negates.
I think there is a bug with meter not resetting or filling wrong, because my group had situation with pillaging phase but meter was full or stayed near -full already before summoning next wave.
The real problem here is that wave meter also relies on class setup heavily. Funcom has designed a mode that 4 out of 12 classes are literally trash in. They should have much more carefully buffed those disabled classes so each player and toon can enjoy onslaught on an equal level… buffing already super strong aoe classes and single target classes should have been done mechanically different, not adding a RIDICULOUS low amount of ferocity on each of them with the same value across all classes. One solution for the topic here could be that filling rate of wave meter adapts to the class setup and number of players since rather frequently some ppl leave or disconnect and no one is able to fill up. FC itself has limited understanding on class mechanics and balancing as evident on the original values of weapon stats with senseless attributes for some classes. What they however could do is gather data from the leaderboards and adapt wave meter increments accordingly.
but most of theese points would be less important if the boss spawns at the end^^
sure a bad group setup would need maybe 2 waves to spawn the boss but fact is if you can fill the meter in one single round and spawn the boss its way easier. So bad groupsetups are at an even bigger disadvantage if they arent able to fill the meter in 1 round.
I think Aoe classes are overrated atleast until wave 20something. You need max 2 that can do good aoe (sure at higher waves too much single dps in group becomes troublesome) but
single target dmg is also important and helpfull. There isnt a single class that comes to my mind that would be rly bad at onslaught. Its more important that ppl in the group let the classes do what they can do best. (kinda pointless to demand aoe from a sin:D - vice versa i see so many aoe heavy classes going on the skulls and ignoring adds^^)
In my experience groups that go for aoe only dont do that well either.