Tactics can be pretty important on the game (well the old ones especially)... if your mesh of tactics is incompatible, or certain players don't suit the tactics assigned to their line, you can get abused.
Individual players can really benefit or suffer from the role they are given as well.
They take some time to figure out but once you find a general set of tactics you are comfortable with and is well balanced you can tweak individual lines and players tactically.
After a while I used the same basic tactics on the old game for multiple saves and years on end, and just changed for individuals and changed in game depending on the score. (change in games were never drastic, usually just overloading the top lines and playing them more and going more offensive if down, or double shifting best defensive line and shortening the bench ie putting say Couturier, Read and Giroux out in 4th line slots as well as their 'proper' 1st and 2nd line slots, if up by 1 or 2 with less than 15mins left... so the 4th line would not be out in that time and the best defensive players play more.)
IMO the tactics, scouting and training are the three most important aspects of the game for success.
Oh, and on the old games at least 4th lines really did matter, even if they only play 10mins a night... the engine is not an old fashioned GM... so all the useless players (according to the engine! so poor hockey players) are waived early on and everyone stocks up on 4th lines where all the players are capable of ~20 points while playing D.
Guys like Clutterbuck, Gaustad, Fiddler, Martin, Talbot used to be a must have on your 4th if you wanted to do really well... I don't know who their equivalents on the new game are but I imagine guys like: Winnik, Kruger, Gaustad, Gordon, Helm, Wingels, Roussel, Clutterbuck etc are the kind of guys that people should be looking to get for their 4th.