It really depends on what’s level you’re at - all heroes at 3/70 are adequate if you’re in a low enough tier.
I am in high diamond (was 2nd overall today for a while) so I’m going to judge based on that who is good at offence at 3/70 (no one makes the cut at defence at this level)
Joon is at 3/70 and still a beast when paired with Jackal. I have to hide him in the corner when attacking and he’s squishy, but even in the top 10 he handles himself fine.
Same was true of Sartana til I leveled her recently and Victor as well, though he was extra squishy and really benefited from the extra defence - but his very fast speed on attack and decent DOT even at 3/70 was fine.
Frida was just okay - her avg speed holding her back from being good.
Richard at 3/70 is just strong enough to take a hit from most enemies (not the elite snipers) and his debuff works well making him usable.
Azlar, on the other hand at 3/70 dies too fast before his slow power-reduced DOT fires so he’s a weak 3/70 for me.
Anzogh and Atomos at 3/70 aren’t really practical in use - but then, they’re not stellar at 4/80
Which leads to Evelyn, who is very good at 3/70 - I have one fully maxed and one at 3/70 and use them both every war. She’s possibly the best of the bunch.
FWIW to the previous poster - North is more valuable than Zeline imo.