nxml-mode is used for more than editing html. When using XML minor-modes that define their own snippets, nxml-mode may override the relevant snippets or clutter the menu with irrellevant snippets. Can the html-specific snippets either move into a html-mode or web-mode directory, or at the very least get a condition that looks for an element?
(An alternative would be if yasnippet could have a method for turning off major-mode-defaults, but joaotavora/yasnippet#496 )