4 players will be a very long game, ESPECIALLY if it is a learning game. I warn you you to not play a 4 player game with all new players. Just...... don't lol. We played most times with 3 and quite a bit with 4, but at a certain point all the players were 100% clear on basically every rule in the game and knew what was possible to face. In that, after many many many plays, we got 4 players games down to like 3-3 1/2 hours. We took to just having a basketball game or a movie on while we were playing because all of the pertinent stuff for you too see outside of your own turn will happen at the very end of another players turn.
It is my favorite game, but it is not without its problems. The main one being downtime. Every turn is a puzzle that you have to figure out, basically. Some times the answer is clear, sometimes it is a little tricky and sometimes you need to spend 10 minutes replaying your turn 20 times to kill that castle in one attack instead of 2.
The 2nd one being the steep learning curve that extends beyond just the rules. It is a game that is both quite deep and quite complex at the same time. The first 2 or 3 times I played the game I thought it was simply ok. It wasn't until I got a better grasp of everything that was and could happen that I came to appreciate it.
The only expansion you need to get is the Lost Legion, all the others are great to pick up later after you want to try new mages.
If anyone has Tabletop Simulator and is up to try it out or learn before they try and teach, I can setup a game no problem.