First, he needs the new melee modding system like excal / wukong. And for every 150 amor gained (displayed in armor UI), his landslide will also gain 15% base crit chance and status chance to compensate for being unable to use the riven mod This also make it more meaningful to build up his armor meter.
second, he needs a faster way to gain armor...like wukong....I mean.. common. My suggestion would be him casting Tectonic then players press X to consume the rock wall and turn it into 750 armor.instantly. this will make his 2nd more useful.
Third, his 3rd ability need to be cheaper to cast. 75 energy is too much for what it does
Finally, his rumble should have the time limit remove like wukong, Rumbler's attack should benefit from melee mods for landslide. For each every 150 armor gained from either dropped stones or tectonic, rumblers gain addtional 15% crit chance and status chance like landslide (cap at 1500 and reduce overtime equal to his armor UI). Each rumblers' attack will increase melee combo counter for atlas.