Firstly:You can catch lugia at level.70 taking the silver wind from pweter city and then go to the whirl islands. It will help your team.
Secondly:Collect many max revives/revival herbs to revive your typhlosion when he will faint, because he will be the only pokemon which could hit his pokemons.
Typhlosion:@LIfe orb-give him speed
-sunny day-to boost all your moveset
-solarbeam-coverage and deals with his lapras+blastoise
-fire blast/flamethrower/lava plume-STAB-deals with venusaur
-Hidden power [rock]-the trick to take down VERY easily charizard
TIP:You can add focus blast for snorlax but is difficult to chose which move it will replace...
With typhlosion you can take 4/6 pokemon down easily. (blastoise, venusaur, lapras, charizard).
Then your problem will be snorlax who have got high HP... And his rest will make you really angry... Me I beat it with a ''tricky way''. I traded a lv.24 staravia from my platinum with focus sash, endeavor and quick attack. In the first turn he left me with 1 hp and then I used endeavor and after quick attack and bye-bye snorlax...
And ten the level 88 pikachu... Ohhhh... a pokemon with just 300 overall stats... even a level 60 pokemon with a strong STAB earthquake will take it down... level up a bit your Quagsire, give him soft sand and many vitamins to attack and pikachu will be the easiest to pass obstacle.
Movesets for your other pokemons won't help if you don't level them-up...