I like the Barclay Sappers, too. Really good for sieges, both in defence and offence. The Barclay Heavy Footmen aren't bad either. The Ebony Gauntlet KO is quite similar in my opinion and is a good addition to Barclay troops in sieges.
I was pleasantly surprised with the performance of the Heretic Magni, they are really good cavalry. D'Shar Windriders are also quite nice. Hero Adventurers are also something to consider. Haven't seen any Doomguides yet, but I recall they were quite good four years ago and I think you can still upgrade them from Doomseekers (hard to get many of those, though).
For defensive infantry, you'd probably want something with a pike or halberd. Armoured Empire Pikemen and Sarleon Halberdiers come to mind. Can't say how well they perform, though. I haven't gotten around to using many legionaries yet, but from getting on the wrong side of them I'd say they are quite accomplished javelin throwers and have pretty strong shields. Makes them a pain to fight, but probably means they'd be an asset on your team. I guess you can use them both defensively and offensively.