We develop the research achievement of recent work [M. Gärttner, et.al., Phys. Rev. Letts. 113, 233002 (2014)], in which an anomalous excitation enhancement is observed in a three-level Rydberg-atom ensemble with many-body coherence. In our novel theoretical analysis, this effect is ascribed to the existence of a quasi-dark state as well as its avoided crossings to nearby Rydbergdressed states. Moreover, we show that with an appropriate control of the optical detuning to the intermediate state, the enhancement can evoke a direct facilitation to atom-light coupling that even breaks through the conventional √ N limit of strong-blockaded ensembles. As a consequence, the intensity of the probe laser for intermediate transition can be reduced considerably, increasing the feasibility of experiments with Rydberg-dressed atoms.