I've died about 30 times from stupid ass Chargers. Most being 7, least being 3. If you have at least 3 chargers on you when going solo, might as well just quit the mission. I swear, the stagger and damage on these things is OP as all hell. They need to be nerfed, Who's with me?
It's really a much better idea to keep moving and keep aware of your surroundings. Tight spaces are murderboxes for Infested. Keeping on the move and keeping distance are all you can do in situations like that. Also consider wall running to flip over the pile and try get some more ground on them.
Get an upgraded lex with some mods, and you can 1 shot those things without a headshot. That is was I do. I can 1 shot kill any infested with my lex on a regular 3-4 difficulty. That excludes ancients. Those things take a primary weapon or melee weapon to kill.