Early Age.
Tien Chi: 4-5-3-2-3. Strong expansion with either Dual Blessed W5E, or simply with very good Composite Archers (that dominate EA indy). Strong middle game (one of strongest imho) due to wide broad of choices in magic (that allow tailor-made strategies versus different enemies) and very good summonable sacreds. It's late game is not bad thanks to magic diversity, but it does lack true power on Blood, Astral or Death, they dont have access to good Thugs or SC and 9hp mages tend to die fast versus global damaging spells. Broad selection of choices make them hard to learn (and easy to make wrong decissions)
Lanka 5-5-4-4-4. A real powerhouse in the expansion phase with very potent sacreds and good archers. Middle game they have strong and easy "out of the box" thugs, they have worldwide recruitable potent sacreds, access to good middle game spheres (air, death) and excelent national summons. Late game they have powerful blood second to none, and enough death and nature to make them "natural" Tartarian makers, plus their own national blood SC. They are easy to learn to play correctly, and they do a lot of things and almost all of them very well done.
Niefelheim: 5-4-4-5-5. They can expand against regular indies using armies of ONE single sacred. They couple that with skinshifters and Jarls for one of the best expansion rates in the game. Middle game they have a wide magic selection (everything but earth and fire, most of it strongly tied), recruitable Super Combatants, strong troops, good stealthy thugs (the scout
) and access to powerful communions for evocations. Late game they have Blood, Death and some Astral, as long as 30 hp mages and recruitable SC. Their Astral might not be that high, but it is good enough to get started.
Middle Age:
Ermor: 5-4-5-5-5. Yep, they are that good. Powerful bless expansion with ethereal sacreds, powerful middle game with competent mages, decent infantry and excelent units, and awesome late game machine with high Astral and Death. I simply love this one.
Late Age
Marignon: 3-4-5-3-2. They have decent human troops with good morale, good missile and good cavalry. Coupled with properly done Awake pretender they can do nice enough in the expansion phase. They get a quantum leap as soon as they reach lvl 4 (flame arrow), and from that point forward, they only get better: Full access to all magic but nature (which is easy to get from indis), cheap and powerful blood, good national thugs, and the best SC chasis there is as a national summonable. They are trickyier to play properly than most nations though. My favourite nation in flavour so far.
Will add a few more later.