you've had 1000 turns to kill the boss. if you haven't managed to kill them by now you never will, whether you take 500 turns or another 5000. the turn limit isn't your problem.

you're struggling here because your team is made up entirely of support champions, so you don't have the damage output to bring the boss down before their a3 recharges. replaceing one or two of them with dps champs should solve this for you.

It doesn't seem like you will be victorious within the turn limit.  I agree, that is a huge problem for you.

they are the only heroes I have from this faction even though I have been playing for 3 years 

Sinesha can do TONS of damage. She's a DPS hidden behind a Support tag.

Just add a Destroy set onto her, build her for damage, and eventually you will permanently decrease the bosses HP pool enough to take him down within the 12 turns you get between the bosses' A3.

Hope that helps :)

thank you very much, I equipped it with toxic set and it does quite good dmg, the only problem is the affinity, force vs spirit, and decreased the tower meter from the valkyries :D