Let's say they both go after porygon2. Custom spread of 252/100/60 to give same defenses on both side.
252+ SpA Sniper Kingdra Draco Meteor vs. 252 HP / 60 SpD Eviolite Porygon2 on a critical hit: 276-325 (73.7 - 86.8%) -- guaranteed 2HKO
252+ Atk Mega Garchomp Outrage vs. 252 HP / 100 Def Eviolite Porygon2: 172-204 (45.9 - 54.5%) -- 54.3% chance to 2HKO
So yeah. I think there is reason to call difference. Also remember Kingdra fires this off again and is not locked into the move. Chomp is and you can bring in a counter well enough if needed. With full defensive investment (I was too lazy to invest all evs), Chomp isn't even getting a 2hko.
You gave Kingdra a free turn to focus energy in your calculations... Seriously though, I dont understand the issue. To gain a nasty plot boost kingdra has to sacrifice its ability and item, as well as one of its moveslots. What's more, this boost can only be gained once and cannot be used repeatedly to get to +4, +6 like other boosts. What's more, the focus energy moveset is predictable, you know draco meteor is on it, and you know he has no lum berry. Honestly there is nothing wrong with a base 85 speed pokemon with a special attack of under 100 gaining a ~+2 boost...
To put it into comparison, Sniper Crit Draco Meteor is the equivalent of a 140 base spa pokemon after a nasty plot using a 80BP move holding a life orb.
For instance, this damage is comparable (actually a little lower) to Timid Porygon-Z using a life orb + adaptability boosted tri-attack at +2 (a common set that already exists). However, PorygonZ also has 5 extra speed, and hits a ton harder with all of his other moves too. He also has a much wider, and less predictable movepool, and yet only resided in UU last gen. What's more, Porygon-Z will not be crippled by losing its item from Knock off or Trick.
Hopefully this helps to convince you that critdra is really not that broken at all, even though it undeniably hits hard.
edit: in my comparison I had to use modest critdra and timid porygon-Z because otherwise the tri-attack hit way harder. This means porygon-z is considerably faster than the kingdra and hits harder still.
Modest critdra hits about as hard as +2 modest porygon-z if it uses swift instead of tri-attack (lol)