The only ones out of that list you should get to 6* are Uugo, Sicia, Vrask and Frozen Banshee, imho. Probably Uugo first I would say. 

I would go with Frozen Banshee as next 6 star because she is great for Clan Boss

hmm, i would do fb last on l9753 list.  i think uugo 1st as well.  fb is no good dead, i think you taught me that J :)  And only 6star Banshee if booked, pretty much worthless otherwise

No, I think you are confusing the lesson I taught you Trips.

I always build the damage dealers up first to provide max damage.

6 Star Frozen Banshee with Lifesteal Gear + Warmaster will self heal to max in Clan Boss.

6 Star Frozen Banshee will do far more damage vs. 5 Star Frozen Banshee.

The only time FB will die is when the CB ramps up to high damage.

By the time the Clan Boss ramps up his damage to high, The whole team will die. 

I build champion's up in the following order:

1st - Campaign Farmer -----> AOE Damage Dealer -----> Viking is using Elhain for this.

2nd - Clan Boss Team ------> It will have 5 heroes -------> I build them in below order:

A ---> Damage Dealer -----> This hero is the Poison hero - Kael or FB or Another Poison Hero

B ---> Attack Down --------> This hero is to keep the above hero alive doing damage longer

C ---> Weaken -------------> Some newer players don't run this unless there starter is Athel.

D ---> Defense Down ------> This hero is to improve the Pyschical attacks Damage.

E ---> Support -------------> This hero tries to keep the team alive or cycling moves.

The Supports are built up last because they often can function at level 50.

They don't always need to be max level in order to do what is required of them.

If the OP Starter was Kael, I would agree with you & L9753.

If the OP had Kael at level 60 instead of Elhain, I wouldn't build Frozen Banshee.

I wouldn't build her because in my mind Slot A has already been filled.

Slots B, C, D, & E are still empty.

I would move down the list to fill the Empty Slots before trying to Improve filled Slots.

The OP has no Attack Down hero ---> Can't fill Slot B move to Slot C

The OP has no Weaken hero --------> Can't fill Slot C move to Slot D

The OP has 2 different Defense Down heroes Uugo & Warmaiden.

I would tell the OP to pick 1 of them.

If the OP was to pick Uugo, It would be fine to me Slot D would be filled.

The OP has Vrask as a Support for Slot E

All the Slots have been gone through 1 whole time.

I would start over from Slot A to see if I can improve on what is already there.

At this point, I would recommend building Frozen Banshee to replace Kael.

In the OP situation, none of the above happened, The OP picked Elhain.

Elhain is a Damage Dealer, but has no business in Clan Boss

The Damage Dealer the OP would want is a Poison hero so Frozen Banshee is the one he would want to build up.

After writing my above message, I went to get something to drink.

I came back and I think I realized why Trips is being confusing.

Trips confusing the way I do Dungeons vs. Clan Boss.

In Clan Boss, you build up the Damage Dealers so you can put them in Lifesteal gear with masteries.

The Lifesteal gear + Warmaster or Giant Slayer allow the hero to max heal to stay alive.

Once, you finish your Clan Boss team.

You move to Dungeons.

Most of the Damage Dealers you use in Dungeons are the ones you previously maxed out in Clan Boss.

This means when you get to Dungeons - Your order of leveling hero's ends up flipping!

For Example: Lets say you have the following Clan Boss team:

A ---> Damage Dealer -----> Kael

B ---> Attack Down --------> Jareg

C ---> Weaken -------------> Athel

D ---> Defense Down ------> Warmaiden

E ---> Support --------------> Apothecary

Now you go to Dragon: The skills you can use for Dragon are the following:

1. AOE Damage Dealer + Poison -----------------> Kael

2. AOE Defense Down ----------------------------> Warmaiden

3. Turn Meter Filling ------------------------------> Apothecary

4. Block Debuffs / Remove Debuffs on Allies

5. Revive

You often don't use a Remove Debuffs hero in Clan Boss.

You often don't use a Revive hero in Clan Boss

This means your team is half way built, but your lacking champions.

The champions you are lacking are support heroes.

This is why your order of building flips on itself.

This is where I say the Phrase "A Dead Hero does Nothing."

I would definitely go with Sicia 1st for dungeons and arena. Then I would recommend Frozen Banshee for the clan boss. The Clan Boss is a great place for amazing ressources (depending on RNG). Also I would make sure to max out Scyl of Drakes when you receive her from the login program! 

Thank you for the replies guys! Will likey follow Benzoboy's advice just because Sicia seems more versatile than Frozen Banshee, then I'll do Frozen Banshee (and recently attained gravechill killer) next. Also got Kael and several more epics and rares since posting this, but nothing that seems quote as good as the ones suggested. 

After Frozen Banshee, Uugo will likely come after since she's widely considered one of the best epics in the game and I could use a solid support for my teams.

Edit: The other epics just in case anyone is interested;

Mausoleum Mage, Corpse Collector, Romero, Missionary,Souldrinker, Grizzled Jarl,Necrohunter, Quargan the Crowned, Steelskull

All the above is great advice. IMO I'd go with Warmaiden for the defense down. She is good in a lot of areas of the game. I 6 stared and fully upgraded her and she is awesome in Arena, Dungeons, Clan Boss and Faction Wars. Zargala would be a better replacement if your lucky enough to pull her. FB is awesome too, I have her at 6 stars for Clan Boss. She's also good at Boss battles but situational. Sicia is also situational. At the end of the day - take a look at what your missing in your current team and go with what makes sense for your account.

Sicia is more versatile than FB, but then FB is one of the most specialized champions in the game, so that's not saying much. Since your first level 60 is already a nuker, the second one should probably be a healer or a debuffer, if you have good options - and what do you know, Uugo is both of those things. I think Uugo before Sicia makes more sense, but even if you do Sicia first, then do Uugo second. Also, don't do Gravechill Killer at all, you don't need her for anything. 

Mausoleum Mage is very good as well and Quargan looks promising.