Blending usually adds complexity and depth. But it should be clear on the label that the wine is a blend, and thus a varietal should contain 100% of that variety. Some of the greatest wines in the world are blends, in particular the red wines of Bordeaux which can contain Cabernet Sauvignon, Merlot, Cabernet Franc and Petite Verdot. At one time Cabernet Sauvignon was considered the best of these and many new world winemakers thought that if the Bordeaux wines were wonderful with 60% Cabernet, then a 100% Cabernet would be even better. The benefits of blending have not been lost on new world winemakers. The Meritage organization trademarked the name Meritage for US winemakers to use on wines blended from the classic Bordeaux varieties. The name implies Merit and Heritage. The self styled 'Rhone Rangers' are Californian winemakers growing making and blending wines from the classic Rhone varieties of Syrah, Mourvedre, Viognier, Moussanne. And they're copying the Rhone habit of blending a little white Viognier in the red Syrah.