Circus came in two flavors. One was full circus where you used 20 runes from any faction and didn't get a bonus. Then there was 10/x circus, where you used enough runes from one faction to get a bonus. KF was the most common because it boosted speed by 1 in half faction. This was before battle group size went to 30.
The problem is that every deck becomes a "best of" deck. Pretty much every OP champ rolled into a ball is worth giving up a bonus. Back when there weren't many runes, it was fine, but now it's a bit much.
I have a st/x circus deck using almost all of the Nora gems and the crystalline champions. Probably wouldn't be competitive, but it it's fun to use in single player.
I have an all factions deck with all my favourite champions from each faction. Mainly for fun. For new players, it is actually the first kind of custom deck we can form from buying just 3 packs. Good to setup a place where non FF or split decks can still PvP. Should still keep Training ground to the rotating pool of constructed decks though. Feel that Circus deck / Anything goes can be apply for unranked custom matches. Btw we still get shrine bonus n avatar even if a faction doesn't make up half the deck. The faction with highest number of runes will get its half bonus n avatar.
To be fair, there were also those rare (iPox) decks where actually pretty cool stuff happened in circus. Sometimes those "cool" things would later be relabeled "exploits," but still, you got to see something new.
