If you want something easier to amass, try the Mercenary Komtur. He's only tier five, and he has six Power Strike and the Coat of Plates (52 armor). He upgrades to a tier six infantry, but the tier six upgrade is pretty underwhelming.
The Femme Fatale (Upgrade from Maiden, which upgrades from the Nurses you can find in taverns) also has six power strike and is a tier five infantry. However, her armor isn't as good as the Komtur (42 armor)
Of the three final tier units you listed, I like the Rhodok best - he has the best armor (56 to head and body) and can get the Military Pick, which lets him chew up other armored enemies. This make him (IMO) the best melee infantry in my opinion. The Kenau is nice (and has 66 HP), but she's also mounted, so she actually costs around the same as a tier seven infantry. And her weapons aren't great.
And even though you said you wanted shields, I'm still going to mention the Mercenary Doppelsoldner, a tier four infantry with five Power Strike and equipped with some of the nastiest two-handers in the game, including the Ornate Zweilander, a weapon with 55 cut and 160 reach.