Maybe 10 years ago players used to play defenders like this, I agree it's THE way to play defender. You forgot DN when shelter ends (prevent shotta temp from DPP lol) but beside that I agree. yep it's sad to see only a few classes played. I really hope the balance patches will turn the tide (one can hope).
Warlock magic push works as a flow-disruption but the rest of warlock (CC) skillset is mainly single target focused (be it that the CD's are low so you can vs. 2-3 players because CC skill duration >>> skill cooldown. Defender has more AOE focused CC but shorter duration, Both skillsets are very good though.