change Eva to Lumina. If all not yet orange, time your raff and jugo ulti to leech heal themself. If severely underleveled, maybe not really a good lineup.

The extreme exp cot is too damn super hard compare to gold ... 3 aoe disable there, only manage to clear once per day and the second round are too damn hard to pass for me.. no idea why.. tried all the recommended lineups but cant, pbly my heroes are not qualified yet...

Have found out this is the best lineup that able to pass with minimal rate within my heroes pool :

Pandor raff bomo medu hyral

Depend on dogde and counter disable to win but kinda hard 

Extreme Cot Try use
Barbaro + Mage Team [Hyral,Abyss,Lucia,Bomo]

works well for me btw what level are u?

Use pure magic team works well for high level. Abyss, Lucia, Bomo, Hyral and Ember. Before this i used to replace Ember with Panda which is excellent too...

you dont need so many exp pots, when u r lvl 90... u have tons of it there, i skip cot exp when all open... no use at all... i almost lvl90 all my heroes includinng those that i dun use like axe buster etc etc...

try
hyral eva lokz bomo abyss - for avg team
eva lokz booster lucia lucas - for 2 front healer with tons of illu
eva lokz abyss lucas grim - for uldor and ember team
hyral eva lokz grim lucas - for high physical hit all team
eva lokz booster grim lucas - for super tanky double front

then once u reach 13, 3 more stage to go u can use sub team to die a few in order to pass it with lesser time.... please take note of the timer.

no idea -.- i havent try other tank. lucas + grim = keep every1 healthy and reduce physical hit from heroes like medusa and lumina.  maybe u can rely on abyss, any heroes with self heal is kinda good for tanking nightmare cof becoz it lighten the shoulder of eva...

should be ok, just the unit u heal become less tanky only.

When they open nightmare i also haven't have lucas yet. So i'll use hero like Abyss, Lokz, Eva, Bomo and Hyral/medusa. Sometime swap into raff (counter uldor and ember) depending on opponent hero.

overall just keep try only... 1 good part of grim is he heals and can snipe off low hp heroes. example when hyral/abyss ulti, u can observe which hero low hp and wanna 1 hit ko him. most of the time i pair grim lucas booster ... booster ulti 1st and hit down hp of front tank then follow by grim ulti... this way u can kill annoying tank like lucas.

I'm pretty sure I will give to lokz