really? i don't know because i challenged the gym right away. after the fight i can seem to transverse anywhere without any problem
btw you should use that one turn-sturdy to thunderwave it, your pokemon will move faster. I have lucario myself and drapion, but i refrain from using it because of the earthquake high strike combo. thunderwave it then use misdreavus with perish song to end it, or any pokemon with destiny bond. pretty sure your untrained misdreavus will move faster.
here's my experience.
i only use 2 pokemon in this gym, greninja and galvantula. from the start to midway, i used galvantula. the last 3 pokemon i use greninja with ice beam. one shotted talonflame with surf. For mega altaria, i used ice beam from greninja. luckily it got frozen with 10-20% HP. She ran out of hyperpotions and boom. The first time I win a gym with just one KO. 6-1 GG