Well for me i’m in process of doing my shinobi since i already have dragoon1 and fencer2 but i will explain a little of what i think so far about swordsman shinobi since at least with swordsman alone i can say that i have a lot of experience.
i believe that shinobi is really strong as a class but right now we simple do not have a good “filler rank” to put him in the main builds of fencer-dragoon-doppel and if you try to make a shinobi “first-only” class at least for now you will be a disadvantage if we compare with the 3 previous classes but let’s be true the future of shinobi also lies with dragoon or fencer if you choice to go a spear or a swords type shinobi so by the end of it you will also choice one of both builds and i do not think that shinobi would combine so well with doppel like he would with both previous build but still can be a perfect way to use it but if you choice to go doppel i believe that murmilio will be better if that jump of his is not locked in swords/shield stance.
So by the end of it is just a matter of choice, you will take shinobi now and finish it with a fencer or dragoon, or take them first a finish it with shinobi.
Be aware that , i believe a spear type shinobi would offer more ability to adapt the build in the future:
you could only take hop2 and dragoon2 to complete the set right now and by that you will be at rank 9. so you would still have a way to choice dragon3 or a new class in rank 10 without even the need to mention that with this build you would have a lot of choices to make the build more your style, and mostly the shinobi you like.
with the fencer one: you would also finish “only” at rank 9 too, since you would need rank 3 on fencer but it the choices on early rank it is a little weak in long run if we compare with spear type.
So by the end of it is up to you, if you choice to go shinobi now you must end with fencer or dragon if you want to take the most of your shinobi, but if you choice to take him later the IMC may release new classes to be more of your liking.
and a side note: if you want to create a shinobi first class and finish it later with dragon or fencer, i would recommend you to wait a little more ,maybe until rank 8 is out, since they seem to be buffing the number of clones skills shinobi can copy or they can even buff swords3 even more to make it useful.
Now if you want to go the path of shinobi-fencer, i would recommend to go for highlander2 barb1, highlander3 is strong but with fencer you would not need to armor break, and barb1 would allow you to have the 50%slash bonus for moulinet+ clones and pierce armor break+kunai+stagger effect from crossguard and of course the slash type skills from highlander too< this one of course will focus on dex >
the spear path is the basic petal1 hop2 corsair2 shinobi and finish it with dragon, this path seems to be the best one at pvp and the ones that most people likes, but is not the one i recommend for PVE build.
for PVE “only” shinobi build, i would go for petal1 hop2 barb1 doppel shinobi>>>dragoon(rank8-9) < this one of course will focus on str con, the bushin may not have enough hp without dex i do not know because i’m not on rank 7 yet but i still believe that you will be able to use the combo well>
i do not believe that i need to say of why this build is better on PVE than the previous one, cyclone + barb slash debuff is already a huge damage bost that can match the hexan dropper and it is a AOE kit that you lack , and of course DOV that will grow with your character forever but with it you will complete lose the pvp aspect of corsair, so choose well.
edit: i must say that with the aspect of shinobi i even think that my “PV
E” only build will work better in pvp for yourself than the previous one, since the utility in pvp that corsair provides is more on a teamplay scale, where with shinobi-doppel with cyclone plus the invi, that allow you do atk, would be a greater finish.