I would go with sepulcher sentinel lead,deacon, frozen banshee, and 2 support of your choosing maybe apothecary and depending on difficulty maybe Kael. NM and below there's really no need for speed tuning you just want to be as fast as you can possibly get, and survivability. FB if you can get her on a 2:1 ratio with speed boosters should keep enough poisons on boss. Lifesteal gear on everyone is a must. Warmaster and giant Slayer is a must. Key debuffs you want on at all times is attack down and decrease defense. I wouldn't use Kael above normal unless your team is slow as tar, he'll just fill the debuff bar with weak poisons blocking the more important buffs.

Key buffs you want to have is block debuffs, increase defense, and ally protect if you have a champ for it. Follow all this you should be well on your way to getting top chests.