I think that the notion that EC use an increased Nr for their vertical Cat A profile to increase lift is a slight misconception. Although not denying the facts as stated by Nick (obviously they are correct) in the case of such profiles the weights are so restricted that lift, per se, is not the issue; it's rotor energy.
EC us the high Nr to increase the rotor energy for both the rejected take off and continued take off cases. In the former case, it allows the high rates of descent, that develop from a reject close to TDP, to be arrested, and in the latter case it helps minimise the drop down following a failure immediately after TDP.
In the case of the EC-155 it is the rate of descent in the rejected take off that is limiting the maximum TDP to 100 ft and the RTOW (1000 ft/min is common).
By using the increased Nr, they are also able to modify the HV curve and this allowed them to develop the 'increased slope' (short field in plain English!) procedure, whereby the a/c is allowed to start climbing sooner than would be the case with normal Nr. Similarly, it helps bridge the 15 kt gap between TDP and Vtoss. It is also a requirement for the offshore PC2e procedures they were developing last year.
By way of an example of the difference, I used to demonstrate failures in a 6 ft hover with normal Nr vesus at 10 ft with increased Nr, with no collective input, to illustrate the benefit. In the first case the low Nr audio would sound before ground contact, in the second case it would only go off once collective was applied to cushion the touchdown.