So I was going back and playing some Legacy strikes. It was all fine and dandy until a Level 17 player appears and pulls full damage numbers with abilities and Fist of Havoc.
They're three total levels below the base suggestion for the playlist, and also surviving better than I am at 392 on a Level 40 character. None of their gear should help. I figure this person is using the Iron Gjallarhorn (because the skin takes away the level requirement), but their total light level is 161. That should be impossible by my math even with IG equipped.
So I look at their character, and apparently the sparrow racing gear also lacks level requirements. This player brought a 400 light IG and 400 light SRL boots into a Legacy strike. At an average of 100 (defense or attack) on their other gear, this person has 600 light value that they shouldn't have access to at this point on their current character.
Split this 600 light value across eight pieces of gear, and this adds up to roughly 75 damage/defense per item equipped (artifacts aren't included). That is approximately 12-13 levels worth of an advantage.
I know that PvE doesn't matter as much in the eyes of the players, but I suggest that when you infuse something into this gear that's merely aesthetic, it's assigned a base level of 20 (at least). If it's over 335, make it a base level of 40. Players shouldn't be able to equip exotics and legendaries at 400 light that early and play things that should be impossible according to the damage tables.
(I'm honestly concerned about balance. This isn't based on anger or jealousy at the player on my part.)
Because it's a legacy strike, they were created with the year 1 leveling system. When they switched the leveling system for TTK in year 2, it made the year 1 strike/mission level irrelevant. This is especially telling when you factor in that all of the year 1 gear had their strength basically cut in half in favor of TTK year 2 gear.
Seeing as you're talking about a level 20 strike, I assume it's The Undying Mind. Factoring in that the final mission of vanilla Destiny is at level 17 or 18 and the enemies are at 100 light tops, even without his two 400-light pieces of equipment, level 20 Undying Mind should easily be able to be completed by a team of 150s (taking away the 12-13 light his 400 gear got him)