Malrath is an amazing arena hero, one of the best imo. But you can't use him in the front against every team, especially on defense.
Anyway, if you can't use the malrath/sumiko strategy yet, I tried some different stuff. I remember at the time I didn't have Sumiko yet, so Serafine was the key. I did use some P2W heroes to improve the chances of surviving, but it was serafine who did the hard work.
I tried to use a similar strategy, but using only heroes that you have upgraded. I got this:
The idea is to have your hurok ult first (95% of the time he will target the other hurok), if the other hurok gets a ult on your serafine you can quit. Then you need garrick ult+serafine to kill ezio. If you don't have garrick's buff yet, try to hit the other opponents. If you have the buff hit ezio or the others, doesn't matter, just don't hit PoP when he is alone on the left side of the screen.
This strategy, with these heroes, is not terribly effective when compared to the malrath/sumiko strategy, or using serafine with a different comp. You need some luck with the ult timings, but it sometimes works, sometimes doesn't.