Shen landing 2- or 3-man taunts and can shield with his ult is pretty baller at it. He's also really only banned by people thinking the meta's the same as SR.

Botrk Frozen mallet some atk speed mobility armor or mr and more damage with boots to top it off

I solo queue quite a bit, and tried some different ADC. The conclusion is that ones with built in escapes like ez, corki, vayne, cait are far more viable in PUG games than ones that don't have that escape. There are just so many gap closers that get a lot of play time in blind pick that its hard to play ashe and be successful. Also, playing ADC is really team dependant. You really need your team to protect you which is hard to coordinate with randos. However, in arranged team it could totally work if you had a teammates to peel for them like cho, singed, malph, lee, jayce ect.
tl;dr adc with escapes viable in solo queue, all viable in arranged team

isn't the eu meta for Treeline ADC+tanky support top, AP bot?

Vayne is pretty good!

no RADC(Ranged AD carries) are not good in TT. they are a pain to get up to speed and if a team fight can help out with the damage distribution. if there was 2 AD bruiser and a AP bruiser a lot of skill shots and damage can be blocked and spread out among the team(if played correctly)

strat works like this
1 AD bruiser go straight assassin
1 AD bruiser go tank
1 AP bruise build a decent amount of Magic pen

doing this make the other team favor Armor of MR
making your AP do tons of damage
and if they don't build armor your Assassin does tons as well