11C is not really all that cold. With a neoprene drysuit, you shouldn't need all that much.
But, it really depends on how long the dives are that you will be doing, which you did not say.
For a base layer, I do not use or recommend Merino. I recommend Merino for a mid layer.
For a base layer, I recommend the Seaskin Tech Base shirt and leggings, or the Fourth Element J2 base layer.
I have been using the Seaskin for years and it works very well for wicking moisture away from your skin so that you stay feeling dry. It is also very inexpensive (relatively speaking).
I just got a 4E J2 base layer set. Only 1 dive on it so far, but it also seems to work very well for wicking. I partly flooded my suit at the start of my dive yesterday. Didn't have the zipper that last little bit shut. I proceeded to dive anyway and ended up feeling warm and dry the whole dive. The water was 12C or so.
For mid layers, I have or have had:
4E Arctic shirt and leggings
Seaskin 150 and 250 undersuits
Waterproof MeshTech 3D shirt and leggings
4E Halo AR suit
It is hard to say as I have not dived them all directly back to back. But, I feel pretty confident in saying that the Halo AR suit is the best of the lot. Very warm, and also very low bulk. And it will absorb a decent amount of water and still keep you feeling dry and warm.