Why Xerath's Ult Needs to Change

I have been playing Xerath since long before the rework, and I have to say I like everything about the rework except his ult. His ult needs to change and HERE'S WHY:

During an assassination Xerath cannot squeeze his ult in with a E-W-Q, without the ability to dodge or cast cc it becomes very easy for your target to avoid the ult's damage and guarantees that your target can hit their own abilities.

During a team fight Xerath's kit can deal up to 500 more damage, is easier to land, doesn't require him to become immobile, and has cc. If you are close enough to use your other abilities, it is hard to justify an ult.

Before a team fight Xerath's ult does not have enough area to get hits on champions that aren't distracted. If you catch them by surprise it is possible to guarantee one hit, but then they know your team is engaging.

After a team fight Xerath can use his ult to clean-up champions, but the team fight has already been won and this has limited value. Additionally unless your team is chasing down your target, it is again very easy to dodge.

While I won't dispute it has its moments, it feels very clunky and really differs from his play style. Instead having an ability which is continuous with Xerath's kit would be huge. Abilities such as:

-Toggled damage amp (like his old W) -Same Ult with access to kit and increased AOE at reduced damage and range

Any sort of change even an adjustment to the current ability would greatly improve the fluidity of his ult.