Hey Zero Sea, big fan of your tactics for a few years now, they brought me a lot of fun and trophies so thank you and i mean that... this year i'm really enjoying the attacking side of 3-4-3 (not using the newest patch) so this is my feedback of this tactic after several seasons... offensively its excellent, it's a shame that a lot of it depends on the corner cheat but it's still very good..
But defensively it's all over the place, even though I had runs of 10 games where i kept a clean sheet... the setup used for defending corners is just abysmal, there are several rock solid setups out there that people probably already know about so it's an easy fix.. but the most important thing i feel is that backline of 3, i think it can be set up a lot better... The majority of the goals that i concede come from very simple crosses after my left/right CB get dragged out of position, so there is nobody left to defend against them.. you have made some very conflicting instructions here, you put all 3 CBs on "Hold Position" but the left and right ones are told to "Close Down Much More" while the middle CB is told to "Close Down Much Less".. so those instructions are in direct conflict for the left and right CB and they get dragged out of position which creates A TON of clear goal scoring chances for the opposition, so a very good GK with amazing reflexes and one-on-one's is absolutely crucial.. This defensive flaw gets extremely highlighted away from home in Europe where teams can score against me extremely easily, I had many results like 3-3, 4-4 etc.. I personally believe that it's very hard to win away from home in Europe against the biggest teams by using 3-4-3 just because of CB instructions..
I haven't had a lot of time to tinker with the backline to try and improve it but i'm pretty convinced that there are better ways to defend with a backline of 3 than what's being used in this 3-4-3. When you look closely to how those guys defend, it's obvious that they don't mark anyone, but more importantly they run around all over the place and the whole defensive shape goes out the window when they try to prevent crosses and get beaten way too easily by wingers. It's a very clear pattern, when a simple cross comes either from deep or the byline i already know it's 50/50 that i'm going to concede. Getting a top goalie with great reflexes has been a quick fix for this so i often get clean sheets, but the goalie has to make quite a bit of great saves from point blank range for me to do that.
If you or somebody else can shore up the defensive trio of CBs then this tactic would be truly amazing, and people wouldn't have to resort to 4-4-2 or 4-4-1-1 for tough away games. I honestly believe it can be done.