Thats pretty interesting actually, many actors have demonstrated a greater "emotional range" during filming after they've quit cigarettes
As for other "Trek Smokers"
William Shatner
James Doohan
Walter Koenig
George Takei
Brent Spiner
Marina Sirtis
Nana Visitor
Colm Meaney
Armin Shimmerman
Tim Russ
Roxann Dawson
Although i'm not sure if any of them (Shatner and Doohan, I know quit in the 1980's) still smoke
One you left off is Ethan Philips (he's seen on the dvd extras smoking after getting his prosthetics removed and leaving the studio) though I am surprised by the inclusion of both Russ and Dawson.
BTW, where did you find out about all the other actors who smoked?
I'm not entirely 100%, but i'll try and explain, in one of Shatner's autobiographies he mentions GR banning the cast from smoking on set between takes (as GR had a particular dislike of smoking),
*James Doohan mentioned that he gained weight in the 1980's as a result of quitting smoking (Doohan's cigarette case also saved his life when a bullet meant for him hit his case and bounced off)
*Don't ask why LOL!! but i confused Walter Koenig with De Kelley (
http://www.trekcore.com/specials/rare/meyer_kelley_smoking.jpg)
*George Takei was once upon a time a smoker, but quit and actually made an audio "Stop Smoking CD" to encourage others to quit
*Brent Spiner and Marina Sirtis would chain smoke during the first few season of TNG and decided to attend the same hypnotheraphist with the intention of quitting,
*Nana Vistor, IIRC quit smoking when she was pregnant, however again, IIRC a holodeck version of Kira is seen smoking,
*Colm Meaney smokes (
http://www.indielondon.co.uk/Film-Review/three-and-out-colm-meaney-interview)
*Armin Shimmerman mentioned that his "unique voice" may be due to his smoking habit
*Tim Russ occasionly smokes during his musical performances
*Roxann Dawson, theres a couple of pictures floating about (
http://celebsmokers.altervista.org/thumbnails.php?album=1807)
*Ethan Philips, I wasn't sure about, however thinking about it i'm pretty sure he does
Hope this helps, its not exactly common knowledge, but if you check out some of their more "personal interviews" (ones about them and not their characters) they will usually mention past and present habits, etc