Hawheyesatx - I don't have any personal experience with the 444 at all. However, I do have a good bit of time and several trips to Namibia with both lever and bolt actions in 45-70 and 450Marlin. I even used my lever 450 Marlin for the PH school in KZN in 2011, and we have taken a LOT of PG with levers and bolt action Siamese Mousers in 45-70 and a custom Ruger 77 and a Win 70 in 450 Marlin. We've take multiple species of PG from springbok, blue & black w/b, red hartebeest, gemsbok kudu and up to plains and mountain zebra out to 170m or so without any issues at all. Bullets have been simple old Rem 405's to 425gr Cast Performance WFLN in the lever guns at 1925 to just over 2000 fps. The bolt guns we run 350gr TSX at 2200 fps and 325gr CEB solids at 2350fps.
Based on that, in my opinion, IF YOU want to take your 444 Marlin to Africa on PG safari, by all means do so. I would caution you to keep species under zebra size and impact distance around 150m or under if possible. With a good flat nose hard cast at max velocity, I'd say even eland would be fine within 125m or less.
As other's have mentioned, it "might" be capable of successfully taking DG under "just the right circumstances", it's likely not going to meet the minimum 4000 ft lbs of muzzle energy that most countries require for DG hunting.
If you'd like to make a PG trip with your lever gun, I'll be more than happy to go with you and use one of mine. We could even put together a little "lever gun only" trip for 3-4 more like minded lever lovers.
Michael