It's a character-side buff, not element-side. Ergo, its ceiling will be lower. "Ceiling" refers to the ideal long term where you have a full SR/SSR weapon grid of one element, all with Assault skills of lvl 10-20, and thus you really want element bonuses instead of more character bonuses.
Also, since it requires your team to be composed of at least 3 different elements, it assumes that members #4 and 5 are non-factors in raw DPS. They are forced to contribute through supportive skills.
The Lilim series is meant to be an option with a nice floor (that is, decent power relative to low investment/requirements) to people who can't yet put together a true mono-element team, so instead you fall back to either a dual-element (Apocalypse or Phoenix, basically) or a faux mono-element setup.