Ideally synergy system would be reworked to allow choice of synergy and a greater build diversity
A synergy system based on skill affinities would solve so many issue brought by the horribly lazy 1.10 synergy system
Taking your previously mentioned hammerdin build, since blessed hammers is a magic spell, then it would be able to synergies with other magic skills, holy bolt, sanctuary, foh…but teeth, bone spear, bone spirit, berserk, magic arrow, guided arrow and VIce versa
That would open up choice for synergy selection, widen build diversity, improve CTc, improve charges, improve oskills