Problem with the truely synergetic squads: they tend to be rather slow, which is why people (myself included) generally don't put them as helpers
My counter squad (Hypericum, Anemone, Mirabilis and Rose for Counter, Dahlia for ATK debuff) is only 471 speed
My trigger squad (Cymbidium, Justica, Apple and Cyrtanthus for increased trigger rate, Fritillaria to leech on all the triggers) is only 474 speed.
On the other hand, my front tanking squad (in my signature) is mostly about being fast and small pest damage reduction/nest heal. Not really synergy, more about strategy.
My second squad which has Dipladenia, Dogwood and some girls increasing the sun gem drop is 742 speed. It is synergetic, but not the kind people want. (many prefer to tab out and skip the solar blast thing).
And speed is what people want for farming, not synergy. So you'll really find very few synergetic helpers around the place I'm afraid..