Fernando is only as good as whatever force backs him up in a push whereas dwarf is ideal at setting up cover over a wider area.
Dwarf holds fortress.
Fern is point man / guardian.
Fern is better suited to multi foe close quarters combat (CQC), with the primary fire foe piercing ability to damage multiple targets at once as well as stack punish and bruise foes with fireball.
If the player is good at going toe to toe with many foes and able to mitigate damage to thyself and allies with wisdom, Fernando can work in most games when that pinch of direct firepower and sustained pressure are needed. Fern has solid personal endurance with his mobility and shield synergy as the ult is handy at eating abilities that are designed to end you.
The players use of controllable shield to prevent damage is key to understanding what one can achieve with a shield. Compared to bariks shield which is better for team firepower and duelling foes. Ferns shield is "in your face, preventing you from shooting" and works when rushing a foe as a team.
Best Fernando will use a shield in a firefight as an asset to waste a foes time and position, not just personal or ally defence.
Just because you are not attacking does not mean you cannot hinder the offensive ability of the enemy.
That all said...
I am not exactly thrilled with Fernando's performance, and I am not saying he is the strongest, but for firepower, protection and mobility, Fern and Barik hold the line well enough.
However my gripes with Fern are small, mainly due to the damage/healing indifference of other champions in contrast to his low dps.
I would like to see his fireball apply a store weapon item effects as he has pretty poor utility damage vs barriers, deployables and such, what is the point of a low damage ranged attack if the second it lands its mitigated by enough life rip...
My other issue is that I am not truly satisfied by his recovery design requiring a support to stay fed when his ambient recovery could be better...