Hello DjKeith
Some engineering suggestions for you which come from my experience on my warrior,Sevhen: http://armory.worldofwarcraft.com/character-sheet.xml?r=Suramar&n=Sevhen
First,have a look-see at the felsteel stabilizer and khorium power core requirements for your wish list of future engineering projects. If you don't have those schematics,get them,as it is likely you will get a skill-up point or two just making them to have on hand. Send the parts you make to alt for storage.
As noted,you can farm the Mech Engineers near Toshley's Station in hopes that the schematic for the Felsteel Boomstick drop. I suggest you pick up the quest chain that requires you to kill mobs in that camp,then treat the schematic,should you find it,as something to pad your engineering catalogue. The guns are not cheap to make,mats wise,and if your experience is remotely close to mine (old,high-density server) you will find it difficult to sell them at anything close to what the mats would sell for in the AH. If you have a huge stockpile of mining mats,and no interest other than maxxing out your engineering skill,then that schematic alone can bring you to 375.
You are far better off farming for the Khorium Scope schematic as a tool to level your engineering skillups. I read on this forum that the schematic now apparently drops from the Mech Engineers; at the time I farmed for it,then eventually got it (March 07),it only dropped from one source -SunFury Bowman- outside of Mana Forge Duro. It took awhile -several dedicated farming runs there,as Bowman are fairly rare,and the respawn cycle was slow. If the schematic does indeed drop from the Mech engineers,it makes sense that the farming may take less time,as there are far more engineers running about,and they are lower level,and easier to kill than SunFury Bowman. Still,I caution those of you who consider Lienna's 45 minutes to get it as the average,or benchmark,to reconsider. I personally think he was lucky indeed :)
But as Lienna notes,the nice thing about the Khorium Scope schematic is that it may actually be sold for a modest profit (+20-25 gold over average mats price on your server's AH). Hunters who have spent some time at lvl 70 will upgrade to them from an Adamantite Scope,and for some hunter builds,the +12 consistant damage buff is better than the Kara (Attumen -Stabilized Eternium Scope) schematic drop of the +28crit to ranged weps scope. Note that profit potential on selling the Khorium Scope depends alot on your server. Some engineers anxious to max out their skill (or in need of gold) will sell the scope at well below AH cost for the mats alone. I have seen that on Suramar for the Khorium Scope,and more frequently for the Felsteel Boomstick,which is why I advised against making a bunch of those in hopes of selling them at anything close to mats cost. Again,your server may be different.
There are currently 12,not 4 engineering items which require Primal Nethers.
There are 11 various Epic Helms,and 1 Epic gun. Although my engineer is a warrior,and warriors can wear any armor,Blizz has decreed that he can only make the Plate helms; I know Hunter engineers that would prefer the helm for rogues,but they can only make the Mail Helm. Go figure...In any case djkeith,Primal Nethers can and do drop occasionally from end bosses in normal 5-Man instance runs,so there is hope for you yet. The only advice (pre-heroic) is to run alot of 5-Man's :). Once you are level 70,concentrate on Sha'Tar rep,make revered,then run Mechanar alot. Aside from the guaranteed Primal Nether drop on the last boss (same as any heroic),you can also collect 5 Badges of Justice from a full Mechanar run. 2 complete Mech runs and you can turn in 10 badges for 1 Primal Nether -assuming you lost both rolls for one.
Good luck to you,post back with any questions :)
Otis