you dont use it to engage.. its best used as a counter engage after a team over commits . if you want to use it in lane to lock down for a gank or whatever
i suggest try to use tight spaces to your advantage (pin them against walls ) . what i do to use it to trade with... is when i want to all in for a kill i will ult then e behind them so they are between the ult and the E and as they go to walk (lol so sad they can walk away ) from the ult W into them rooting them and use Q to knock them back into the ult kinda like a big cc chain
but in team fight /ganks situations using it to divided or cut off the team is good to be able to focus down one target as a team... or cast it side ways across a lane as you come in to the lane from the side. but he is meant to be a defensive tank with cc so its basically a counter engage tool