Sorry, but "Eternal said it" does not make your arguement stronger
anyways, jellicent will never beat volcarona because Jellicent takes >35% from bug buzz (and thats not even a fire blast)
Chans+Bliss: allow me to show you +1 LO fire blast
specially defensive blissey (252/252 +spdef lol): 607 Atk vs 405 Def & 714 HP (120 Base Power): 376 - 444 (52.66% - 62.18%)
standard chansey (252/0 neutral nature): 607 Atk vs 369 Def & 704 HP (120 Base Power): 411 - 484 (58.38% - 68.75%)
If you run ttar, then you are probably running sr on it since most people use that sucky mixtar lol
alright so lets just assume you take out ttar to counter latios/latias/insert psychic type here. So lets just assume that you get rocks up with oh, lets just say bronzong. I get a free switch in to 'Top and can use rapid spin. Now you have to set up rocks again, or else ttar becomes dead bait for the rest of the game. literally. So either you bring in Zong again (which is setup bait for a hell lot of the meta) or you let the sun stay up for the whole game. Anyways, I won't use Dugtrio as my arguement, I'll use Wobbufett.
Lets take your terrakion again, now heres your stone edge calc against Wobbufett
scarf terrakion: 357 Atk vs 181 Def & 528 HP (100 Base Power): 211 - 250 (39.96% - 47.35%)
You need sr to 2hko and even with it you don't have a full chance. On the other hand, I just got rid of your counter and now I can plow through your team with volcarona. Also, cb terrakion doesnt cut it because +1 fire blast ohkos lol.
Now lets take dragonite and gyarados!!
dragonite +1 bulky outrage: 472 Atk vs 181 Def & 528 HP (120 Base Power): 336 - 396 (63.64% - 75.00%)
beautiful, you dd on one turn and attack me the next and now you're dead. Have fun, I just got rid of your counter. Bulky Multi scale because otherwise you lose to +1 fire blast.
Gyarados:523 Atk vs 181 Def & 528 HP (80 Base Power): 249 - 294 (47.16% - 55.68%)
+1 bulky waterfall does around that much, not exact but should be pretty close
anyways, as you see, all of your checks are dead. Wat do? get swept? ya
seriously, try volcarona with wobbuffet (god i hate spelling that) and you will see how easy it is to abuse.