Stat wise, my level 20's character was buffed higher than any V16 I have. Not having some skills can make it harder (for example templar not having radiant destruction for burning bosses).
It also matters if the players know what they are doing. I'll take 3 level 10s who have V16's alts and completed every dungeon, over 3 V16's that never completed a single dungeon any day.
I frequently leave groups I get put in when there are low level players. If you aren't even proper level to do a pledge (45 I think.) Im not interested. I will also leave straight away if I see we have a dps who qued as tank/healer. Experience has shown me that it is most often not worth my time. I will gladly spend that 15 minutes doing somthing productive/fun instead. This changes nothing.
@Tsai-NZ As a veteran rank player you will never make a dungeon harder for lower levels! Some of my favorite dungeon runs have been when my VR16 healer is queued with a collection of low level friends on chat looking for a healer and some guidance on the dungeon mechanics. It's very rewarding to experience their reactions as they go through the dungeon for the first time.