I've won octopodes of every background, and I almost never use transmutations, particularly statue form. As Rast says above, octopodes have access to 3/4 primary defensive skills for melee: Fighting, Dodging, and Shields. Make use of them.
However, like other no-body-armor species, you really should be using magic, given that you have no penalties to doing so. Going heavy into any of the good magic schools -- summons, necromancy, hexes, conjurations -- will help reduce the number of situations where you have to expose yourself to bodily harm.
You also have more or less no reason not to have a good stealth score, given the massive stealth apt and native stealth boost on octopodes. You should use that to pick your battles and avoid taking on big groups.
Here are a few morgues for examples:
http://dobrazupa.org/morgue/Lasty/morgu ... 170930.txt -- OpWr that mostly used demon trident melee and death channel
http://dobrazupa.org/morgue/Lasty/morgu ... 013821.txt -- OpAE that found Monstrous Menagerie on D:7 and hard-switched into hardcore summons by Lair:1, used summoning/dtrident for endgame
http://dobrazupa.org/morgue/Lasty/morgu ... 003458.txt -- OpIE using staff of cold / Ozo's Refridge spam backed by throw icicle and bolt of cold
http://dobrazupa.org/morgue/Lasty/morgu ... 023609.txt -- OpAK using morningstar/great mace, no shields by vaults, light hexes/charms magic into Dragon's Call / !brilliance end game
http://crawl.berotato.org/crawl/morgue/ ... 002326.txt -- OpWn polearm focus terminating in vamp bardiche, no shields, light magic, shadow creatures trained at endgame
http://crawl.berotato.org/crawl/morgue/ ... 173818.txt -- OpAs demon blade / shield, throwing, no magic training, no Trog.