There have been certain cases where altair used stealth to his advantage, most of his missions were dependent on stealth, as far as ezio is concerned, his stealth is not irrelevant, to the sole fact he had chain killing in ACB, so stealth was not important, to be frank, not needed infact, as he could take on an army. Edward kenway was a true stealth master, and a high tier notorious assassin, many might conclude his arrogance, but it means little in the haste of battle and lust to smear blood of the enemy. connor was also somewhat efficient, but he lacked the combat skills to componsate within that said category.