Among all the Wizard sets I’ve played (barring the latest addition), I can concur that Firebirds is a terrible set to play with.
I think they should just rework the set’s mechanics because it’s just wonky to have a set’s bonus effect work under very specific or obtuse conditions.
I still think Firebird can tweaked to synergize with Mirror Image in a meaningful way without amping up its damage bonus straight to gazillion range.
Looking at items in the alpha version I have no hope for it to apply.
Infinite upvotes times infinity. (thanks Cantor)
Actually you bought up a valid point on why was Firebird didn’t get revamped until now because it would require them to revamp the set dungeon as well, which is probably something that they don’t feel like to do so.
I don’t mind if they insist to keep the ignite mechanic for firebird, but they should really give firebird a straight fire DPS and DEF without relying on ignite mechanic because it just doesn’t work on low-level difficulty or GR because either the monsters died too quickly or there weren’t enough monsters in the screen to get ignited for maximum bonus or you died (lack of DEF LOL) before they get ignited.
It’d be rad if the ignite counted as its own source of ignition. Basically you set the enemy on fire once and they burn hotter and hotter until they die. This could also be a damage focus for groupmates using fire abilities.
It is a shame that Firebird’s is in the state it is now considering the potential it has.
If I’m not mistaken the set dungeon will not need any changes as long as the revival and the ignition mechanic stays.
So how does the latter stay without making it clunky, well every single attack ignites the mob. Simple and straightforward. This could be used as a debuff on the mobs (trash to bosses) instead of binding it to the players buff.
Examples:
Ignited enemies get’s their max life reduced by 10%. This would make group play easier and thus Firebird’s would get popular…
Ignited enemies takes 10% more damage from all resources double amount from fire.
Now as for attacking, each fire attack could give a buff to the player. Something like the 10 stack buff the new Fragment yields. At ten stacks you get 75% damage reduction and run speed bonus. This could also give a partial damage bonus the total should be small though.
Finally as a six piece the damage buff is finalized. Giving the fire mastery rune might seem over the top on the other hand the 2 piece will probably stay as is 
Set dungeon originally had to be ignition, but they changed it so it could be igniting OR killing 20 enemies in 6 seconds.
So in theory they could change the ignition mechanic, the set dungeon would still work because you’d still have the killing option.
Some form of ignition does seem like the core aspect of the set though. The original version in early RoS had the phoenix revive and an early iteration of the ignition mechanic. Seems like they’d want to preserve that. Maybe in a changed form, but still some type of ignition.
I actually enjoyed when Firebird caused enemies who took fire damage to explode, rather than burn. I always thought that kind of mechanic could’ve been built upon.
But yeah, they could definitely majorly overhaul the set without needing to worry much about the set dungeon, well except for maybe the revival since that it is a part of the set dungeons missions.
Let me clarify, since the ignition will happen with first attack the next part to kill 20 ignited enemies within time limit will be achievable.
That way I suspect that making the move away from the three spell ignition won’t affect the set dungeon but will make a huge change in playability.
Right now the set is good for an easy set dungeon mastery and then salvage for mats.
Other than that I’m no fan of that mechanic, if it stays it could work as proposed in order to be appealing in some way.
Even if that isn’t implementedwhat really matters is a damage boost to fire spells, damage reduction and movement speed.
Well… if we talk about Firebird, how’s this:
(2) piece bonus
Conflagration can stack up to X times and applying fire damage to an enemy refreshes existing stacks.
(4) piece bonus
Attacking with a fire skill reduces your damage taken by 60% and increases your Movement Speed by 30% for 10 seconds. Should you die, a Meteor falls down from the sky and revives you. You can be revived once every 60 seconds.
(6) piece bonus
Enemies affected by Conflagration take XXXXX% increased damage from your Fire skills. Conflagration now also deals XXXX% weapon damage as fire every second and after reaching five stacks the effect lasts until the enemy dies.
This is how I would redesign the Firebird set at this point. It might not be the most creative idea, but it’s simple, easy to understand and fits the “make 'em burn” theme.
As for the figures… well, I guess 5 stacks for Conflagration are fine, and 12000% to fire skills should be a good base. Then, maybe something around 2000% or 3000% weapon damage per Conflagration stack.
Something like that.
Sorry Lexa, no. I had a more direct solution in mind namely @Aly 's, it’s available in another of the countless threads.
The only reason I suggested the above was in order to have a way out of the set dungeon collision that might occur.
Most will agree that we don’t want them burning… we want 'em dead.
Sure but the damage dealt by the burn effect is pretty much a side dish - I used the Conflagration passive for a reason - especiallly if the set makes the passive’s effect stack on enemies.
@Lexa Wait did I misunderstand your proposals?
Answer YES You meant the 6 crit chance passive. I thought it a “name” for ignition.
If so then it is a new favorite, or to be precise one of two.
Post edited 
I like it.