Hegh doesn't mean be dead; it means die. To say He's dead now, you need to indicate the dying is complete. Heghpu' means died as in having completed dying. You probably don't want DaH Heghpu', because that suggests he undertakes and completes the action of dying NOW. What you probably want is just Heghpu' He died, he has died, with the now understood, or maybe DaH yInbe' He's not alive now.
Thanks for the tips; I'm still very early on in the course, and have yet to learn a lot of this. Sometimes the best way to learn is to try, make mistakes, and be corrected. :-)
So the suffix -pu' can be an indication of aspect (or completion), as well as being a pluralizing suffix?
Yes. -pu' on a noun means plural beings capable of using language. -pu' on a verb means completed, or perfective, aspect. There's another perfective aspect, -ta', which means the same thing as -pu', except it carries the connotation of having set out to accomplish the action. -pu' can always be used whether the action was intentional or not.
When I pronounce mogh my mouth doesn't go anywhere near pronouncing any style of English r. Klingon gh is formed by moving the tongue back and down. Rhotic r is formed by moving the middle of the tongue up toward the roof of the mouth; a trilled r (like a Klingon r) is formed by moving the tongue forward and the tip upward. A Received r is the closest to Klingon gh, but it is basically like saying ah.
Klingon gh is reminiscent of a French r, but it should completely lack the distinctive r-ness of it. Listen to this person teaching the pronunciation of French r. https://youtu.be/vv3Y69d4IQw?t=119 When she demonstrates the pronunciation of the word rouge, she says "not rouge [with an American r], not rouge [with, basically, a Klingon gh]." You can hear how Klingon gh is NOT French r. But she points it out because people get confused between those sounds.
The KAG site has a decent example of the word mogh being pronounced (https://hol.kag.org/sentence/mogh), though I think the vowel is being held too long into the gh. But the speaker is clearly not adding any r-ness to his gh. Compare to his pronunciation of morgh: https://hol.kag.org/sentence/morgh