For an indepth analysis of EA Ulm units,
see this thread.
I do not consider EA Ulm weak. It has some problem with its magics, namely low levels but good versatility. It has good units as long as you only use the female units and archers and possibly the iron and steel warriors.
Marverni could conceivably be a good nation to play, but it requires production scales to be able to pump out the good units. Ambibate Noble Warrior is one of the best EA infantry units. If you also have a F9 bless, the boar warriors provide with quite the shock potential early on.
I must say that I have not played very many nations at all, though I have a fair idea of strengths and weaknesses due to my familiarity with the units from making the DB.
I will also note that if some nation does not suit a particular player's play style, chances are that the player will suck with even a strong nation compared to something that does suit him.