Some of the necro debuffs give description changes in lookover. I can't remember the specific wording but:
Wither- "Black aura"
Blind- "Cloudy eyes"
Rot doesn't give a description change but it does let you know when it wears off- ie "xxx is felling better"

No worries, I imagined it would be a pain!

Is it possible to have Rot display the damage that is being done each tick, and/or provide exp for damage done?

I think it should, with the changes NH is proposing to CHR affecting pet stats. Well maybe not the heal rate but the heal amount, to be clear. I assume pet heals have something to do with pet INT so they'd be affected? Yeh, it's INT based. You don't need a ton of int to make it useful, but it's req...

I'm unable to summon the ranger pet/use a soul gem.

When attempted to use the soul gem:
"You must release your current pet before using another one!"

When trying to release the pet (or any other /pet commands)
"You currently do not have a pet!"