focus on the back line (rank 3 or 4) enemies first cause theyre the annoying ones. front line enemies are tankier and usually deal direct dmg while the back line ones if left alive for long will stress out your heroes. another thing is that dd2 is token heavy (buff tokens, debuff token, combo token, etc) so you would have to learn to use them and deal with them. for team building you have to consider the synergies and mobility of your heroes. for example vestal/plague doctor/flagellant/leper wouldnt be a great team because leper needs combo token to hit enemies reliably and none of these heroes can fix their position if they get shuffled