Also take note that if your second skill is in the midst of casting animation and you activate your 1st skill, you will cancel your second skill which lead to damage wastage! Learn to cast smartly both offensively and defensively!
2- Damaging your enemy too much energy without the capability to finish them off, will allow them to proc and cast their first skill on you for enormous damage. This is related to the first point, whereby you have to time your skill cast to interrupt opponent skill cast. Using the same scenario as above, but assume you are on the second battle of crucible of fire and had already had full power on your team from the start of battle. After the second turn (all second ability casted), you activated Noire and Kane's skill which dealt enormous damage on opponent's team. This will fill their energy bar and cause they to cast their first skill. If you time captain's shipwreck nicely, you be able to stop opponent's Captain, Kane and Ember from casting their primary skill on you. Another common example is when you use ember skill and it doesn't finish off opponent, opponent will then react with their first skill most of the time, you dont want that! So many sure when you use ember skill, you either finish off the opponent or have a disable ready to come after it!
These 2 pointers are essential and vital to maximizing your team potential and take time and practice. You have to understand opponent heroes's skill cast sequence and which of your team can be used to interrupt opponent.
3- Learn to bring the right hero.
If you see opponent having a physical team, bring a tank that has the best physical defense, likewise for the other. If you think opponent has lot of crowd control, bring someone that is able to interrupt them. All this take practice, knowledge and also the luxury of having multiple heroes which will all come with time