If you're solely looking to clear maps the fastest, 3x Heaven's Roar kills pretty much everything in the game even with mediocre Matk, so either 3x Agi/Luck/Dex Champions or 1x Agi/Luck/Int Champion + 2x Dex/Agi/Luck Kafras would be absolute god tier. Nothing else clears the map with the same efficiency.
That can be pretty boring though, which is where diverse teams specialized around themes or tactics comes in.
TL;DR Version: champions if all you want is to clear the game fast, otherwise which units are good depends entirely on your playstyle.
The above post was typed in front of a live studio audience.
Are they magic attack based ? isn't that problematic as his intelligence is a bit lacking ?
I thought so too but two things seem to be helping me out. The range for magic strength is much more narrow than physical strength. So a strong physical attack will be maybe 400, 500 with str of 160 near the top of mirage tower. A strong magic attack will only be around 130 with an INT at 80/90. So my Lord Knight even with his paltry magic attack of 50 is still decent enough to overcome so many enemies weak magic defense with those 2 skills.
One of the LK i'm using has SP lowering cards and sword dance up to lv5 with an INT of 60. He either ohko's most enemies or two hits them, even with a strength to fire.