Spellswords have a lot going for them, and their weaknesses are largely shored up by class features. While they're only a 3 APR class, they end up having the best attack progression in the game due to getting an extra attack at their highest AB. As a 30 CL class with haste, they're able to keep themselves hasted nearly constantly. While they're only a 20 AB class, their easy access to +5 weapons, +4 weave AB, and long lasting war cry allow them to operate at WM levels of AB. While they do rely on buffs (as all melees do at this point), breach resistance makes them less susceptible to the pain of breaching (also together with their large number of non-dispellable effects, like +5 weapons, +5 armor). While they only get 8th circle spells, they get a special spellbook that has 9th circle spells at their 8th circle and abj champ is able to skip the 9th circle prerequisite on ESF: Abjuration. While they can't fit WM to get x3 crits, elemental strike and their high number of max AB attacks lets them trade comparable damage numbers.
The class is solid and has a lot going for it. On top of all that though, they also get a max CL disjunction (and from an abj champ, they're also backing that up with ESF: Abjur) that creates a massive tempo advantage against any other melee class. My suggestion is that they lose this feature to bring them back in line with mundanes and other gish builds.