So do think its possible that..

[AzraelX]

I can reach the end the 2.55 by june 19th and blaze through main story doing none of the side quests? And just come back and do them as a machinist/astrologian later?

[Nutz]

Yes, though you'll need some supplementary exp from FATES or extra dungeon runs if you skip all of the side quests. Actually, you might not need much now that I think about it. I leveled my initial class before the weekly challenge log. Make sure you unlock that at level 15 (it is technically a side quest) in Limsa and you can get a lot of extra experience points from dungeons, FATES, and such.

[AzraelX]

Yes, though you'll need some supplementary exp from FATES or extra dungeon runs if you skip all of the side quests. Actually, you might not need much now that I think about it. I leveled my initial class before the weekly challenge log. Make sure you unlock that at level 15 (it is technically a side quest) in Limsa and you can get a lot of extra experience points from dungeons, FATES, and such.

omg i didn't know the challenge log was weekly lol.. i thought it was for the entirety of the game. That makes sense when i would get challenges multiple times. lol wow thats awesome they have that. ff14 keeps getting better.

[Dualblade]

Since you are already 50...you might have to do some sidequests in order to get gear if you aren't already at ilvl 90, but otherwise you should be good to go. Most of the big fights for the story now are the Primal trials which shouldn't be too hard with all the people running them who are overgeared themselves.

[Cakekizy]

You would need to do some sidequests to unlock dungeons for ilvl gear, unless you get it from MB.

[lacrimosaangel]

yup. This is what I'm doing... Though if you want to get high ilvl without MB or rolling in dungeons, just keep running primals and get soldiery and buy the gear from Mor Dhona, it'll get your ilvl up quite quickly. Might not be the best gear in the world but will give you enough levels to do some of the other trials (Odin is next on my list!)

[Niwashi]

You would need to do some sidequests to unlock dungeons for ilvl gear, unless you get it from MB.

Gamerescape's wiki has a pretty good listing of how various content and features get unlocked. For anyone skipping unimportant sidequests, I suggest checking this list to see if you're unlocking everything you want to:
http://ffxiv.gamerescape.com/wiki/Gu...Locked_Content
Not everything listed there is equally important (for instance, some of the minions it lists I don't care much about) but for any feature or content you do care about, it should show how to get it. You can figure out from that which sidequests are important and which aren't.