Yes, they're fearsome. Even when the AI controls them. When I played Greeks and encountered them, the hoplites (not the armoured ones, though) had real difficulties in dealing with them, mainly because they are oversized. Oh, and did I mention that the AI had actually built a lvl 3 Woden shrine....those spearbands kick arse. especially in greater numbers which are easy to obtain even for the AI.
Germans are one of the strongest factions despite being Barbarians. The only perceptable challenge consists in playing on huge unit size: with all your crappy little settlements, it will take a while to level them up as long as you fight on all sides at once, even more so against opponents who don't have similar handicaps.
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