I have done a lot of expirimenting with Lyonar, and these are some things I have found. Second Sun isnt that great. If silenced or displaced ot becomes a 0/8 which is practically useless. Yeah you can Roar it the next turn but there are much better options.
Ironcliffe +Divine bond is super strong so if you are using those as your win condition you shoild be running 3 of each.
You mentioned you were considering anothef win condition, and I think many legendaries would fill in nicely. I really like Pandora with Lyonar because your iorncliffes demand removal, so they are less likely to have a way to deal with it. Buffing the wolves(ranged/celerity in particular) can be devedastating. Divine Bond also works well on Pandora herself. If you list all of the legendaries you have people could suggest which ones to add in.
Jolly Immolation is absurdly good. I think it should be in just about every Lyonar deck. 90% of fhe time you dont even take advantage of the heal, but 4 AoE damage is absurd
Azurite Lion is extremely good. I would reccomend swapping Healing Mystic out for them. They are extremely good early(mana tile hogging/midgame roar for burst) and this deck doesnt have too many beefy targets that will survive needing a heal.
I assume you want Crossbones for Mechazor, but there different options to consider. Sunset Paragon,(additional Sun Blooms), and hollow grovekeeper are all alternatives that can deal with Mexhazor, and still have good value agsinst other decks.(keep in mind you musf place these cards adjacent to mechazor for their effects.) The turn you suspect Mechazor is coming try tl take center board and chain your minions so that you can summon your answer next to it no matter which corner it drops. If you consider running tigers, they greatly extend your reach.
A little bit more lategsme cards would help your curve out as well, and also help you keep more cards in your hand
If you have any questions feel free to ask, I would be happy to explain more in depth