Okay, I’ll write down the rundown on all the potential same rank classes:
Swordsman
Peltasta + Highlander: Bad. SIX stance conflicting skills. An unhappy couple!
Hoplite + Barbarian: Okay.
Rodelero + Cataphract: Bad. Rodelero skills don’t look mount-friendly and you lose out on Cataphract’s 2h Spear Mastery.
Squire + Corsair: Okay. The combo doesn’t give each other anything besides a second bind skill.
Doppelsoldner + Fencer: Okay. Doppel goes well with any swordie class and Fencer isn’t bad at C1, but you would rather get Fencer C2 or an R7 instead.
In general, swordsmen have bad synergy due to weapon type dependency so they have definite problems with same rank classes.
Cleric
Krivis + Priest: Good. Definitely a regular build.
Bokor + Dievdirbys: Okay. Zombies and statues seems like a bit of upkeep.
Sadhu + Paladin: Good. Interesting skillset.
Monk + Pardoner: Okay. Monk doesn’t gain much from Pardoner besides Increase Magic Defense.
Oracle + Druid: Bad. Both feel like preview classes with their larger spell sets. Just get an R7!
Cleric has solid picks overall, so their selections in same ranks are nice. However, specialization is usually more favorable.
Wizard
Pyromancer + Cryomancer: Good. Covers for each other. C2 Pyro and C3 Cryo works out for rank 6.
Psychokino + Linker: Okay. Having one mitigates the other unless they are in cooldown.
Thaumaturge + Elementalist: Okay. You want C3 for one or the other since that is when they reach their peak performance.
Sorcerer + Chronomancer: Okay. Quicken and Haste are effective on Sorcerer’s summons.
Necromancer + Alchemist: Bad. Alchemist brings nothing to the table for Necromancer. Necromancer benefits far better with the two R7 classes.
Wizard has a wide variety of combinations even with same rank, but most of the classes don’t perform strong enough by themselves. It’s really annoying!
Archer
Ranger + Quarrel Shooter: Bad.
Sapper + Hunter: Okay.
Wugushi + Scout: Bad. Scout needs C3 to hold its own.
Rogue + Fletcher: Okay. Still suffers from stance conflict.
Falconer + Schwarzer Reiter: Bad. Companion conflict, of all things.
Archer has several synergy problems like Swordsman does. Weapon type changing doesn’t help at all.
Conclusion
this is a mess
My opinion might be wrong, there could be some good same rank class combos. Feel free to post about it.