Wall plate dimmers are invariably of the "phase control" type - they are cheap & cheerful and essentially vary the power delivery from 0% to 100% for an incandescent device like a halogen bulb.
LEDs do not dim - they are either ON or OFF (they don't dim) - you get the ILLUSION of dimming by using PWM, Pulse Width Modulation, where the LED is switched VERY rapidly on for say 10% and off for 90% which gives the ILLUSION (as your eyes have persistence of vision) of a 10% bright LED. LEDs therefore generally need PWM rather than phase control dimmers.
You can easy see the rapid on/off switching of LEDs by spreading out your fingers in front of your eyes and shaking your hand up and down - the fingers will appear to "freeze" just like in a old strobe light - LEDs turn on and off immediately as they are solid-state devices and have no thermal lag (unlike halogens).
Some modern LED units are smart enough to interpret phase-control and change that internally to PWM, but it's a nasty hack. Just do a proper job and change the dimmers to PWM as well.
PWM dimmers should also work with incandescent bulbs.
Except in the showers, I replaced all our MR11/MR16 lights (52 of them) with 230VAC GU10 LEDs and removed all the transformers (nasty things, unreliable). It's worth noting that LED MRxx bulbs often have real problems with electronic 12V "transformers" as the electronic 12V transformers often require a minimum current draw to work correctly and a LED replacement may be 5W instead of 50W, so the bulb may not light at all, flicker on and off, or "sing",