I don't think I've seen any pros in races like the tour of France wear any wicking base layers, and it gets silly hot. Also they'll start low and climb into the mountains, often you'll see their jerseys open with no base layer. Then immediately after the race they'll get wrapped in warm attire. You'd think this would be a good time to wear that extra under layer but they don't, so that's my thoughts.
For me I'll forgo the jersey and just wear under armour long sleeve shirts, especially in the conditions you describe.