Actually, you should focus if that’s a hero you want to keep, specially the 3* and beyond. Make sure to feed each hero other heros of the same color. That gives a bonus xp to the hero and chance to lvl its special when lvling.
Concerning farming and campaign, I would farm 8-7 for the chance of more adventurer’s kit and practice swords to train more heros and then level more your current team.
Advancing in the campaign itself won’t actually give you any benefits. If you struggling, just let it go, work on farming 8-7, get that flow of items and recruits going and one day when you have lots of energy go back to progressing in the map and finish off the province.
Your main focus should be also working on the city and his buildings. Max lvl every farm, max lvl one of the forges and training camp. Ignore the mines, lvl them slowly when you feel Iron is getting scarce, ignore the tower, just work on the easy and fast lvls while you wait for iron to lvl something else for example.
Getting those training camps going and training lots of common and uncommon heros is how you rapidly lvl your heros. Forges will help with hp potions, arrow attacks and banners, get that going on the side.
When lvling heros try focusing on the 4* and 5*, they are keepers. The other ones will be gone soon.
If you can, replace on if the healers and try having a max of one in your campaign team (def team you can do whatever you want), they also won’t help much in Titans fight.
On that note, find yourself a helpful active alliance, talk about what heros are nice, check out people’a teams, like ACTUALLY read each card and consider why would those be nice together. That’s specially useful and important in raids. You can’t beat someone with close power number? Check the guy out, use that to “steal” and learn some combos. If you can’t figure out how that team is so good, try out one more time and see if it’s bad luck, ask your alliance, take a print and ask us here.
A huge part of this game is about strategy and having a good team, and that comes with experience.
Right now your team has:
Hu Tao: good multi-target hitter with a debuff that helps survival
2 healers: hawk being a big heal and believe being a heal plus dispell. If you can, drop Hawk.
Athena: good sigle target hitter with splash and a defense debuff that will increase other heros damage
Renfeld: single target damage with self healing.
All your problem is too much healing. A new green or red to replace the healer is for best bet. Something with a good damage centered skill.
Other than that, make sure to ALWAYS hit Athena’s skill FIRST. Specially in boss fights, delay other heroes attack skills until Athena has hit. You can also use mana potions to pump her up before using the other heros.
The order should ALWAYS be: buffs, dispells and heals that do not do damage (specially the boosts in attack), Athena, other heros that apply decrease defense, heros that apply attack buff when hitting, all other heros in order of the weakest to the strongest (specially if you have Athena, that way when it’s the last one turn, your strongest, her debuff stack will be at its highest and hit for a lot more).
You do that so you can clean your heroes of any debuffs first (can be done with antidote as well), apply extra attack, decrease the opponents defense (so it will resist less your attacks, increasing your damage done), increasing attacks with the hitters after the defense is low and then having all other heros do their damage and murder your target.
I think I went a bit offtopic… anyway, 8-7, farm thoses kits and swords!