Offensive game changer and all around heroes are the ones you want to focus on. This means they should be at least average speed.
In that respect I would consider the following ones:
- elemental 5* def down: they will make any other offensive hero you to be deadly and most of them also debuff;
- krampus/BK for the taunt;
- gazelle as it’s certainly the most OP offensive hero
- any 5* ailments blockers
- cKadilen : she’s broken in both offense and defense
- any 5* healers that are at least average speed. Their increased survability compared to 4* healers really make a huge difference
- In the current meta Skadi is the Queen and to some extent other minions killers
- I find buff blockers extremely important in offense too, malosi being the best but onyx and in a certain way zocc may also be good in that role;
- blinders (drake/moreau) and attack debuffers are also good to prevent heavy AoE hitters from crushing you
- all 5* cleanser are valuable
Now you have to find the portal that may offer you the most of this type of heroes I believe.