Hello Lionelus, I think you should ask Salvy13 #artyspammer from my  mates if you ever find him in game: he only plays brit and only that doctrine. And when i say only i mean only. Unfortunately he does not partecipate the forum, so he won't come help you here, but i showed him a screenshot and he said if you're not a defensive player RA is just not for you. His exact words are: "RA is not a doc, it's a lifestyle. You must feel the arty, you must live the arty, otherwise you can't understand nor appreciate it."
What i told you is all true, tho it's probably not what you're looking for, i just wanted to give you a laugh
I'm more an offensive player as well, so i very rarelly play arty doctrine, but i can tell you what i think are the main upsides and downsides as far as i know by playing quite often teamed up with Salvy13.
-due to the lack of specialized assaulting units, infantry and tanks, the micro-related playstyle is pretty much as if you were playing without picking a doctrine.
-your howies might be considered good to take down defences but they're not so accurate, and if your enemy starts building bunkers or ambushing tds your 25 pdrs damage output will just get yo frustrated. (Hopefully will be better now that VT ability will be fixed)
-(this one's not very onbjective, a bit "ranty") if your opponent finds out you're arty, he'll probably pick SE or DEF doctrine. In that case his superiority in artillery vehicles ("onehitkill"grille, wespes, hummels) will probably "outbomb" your howies (toghether with everything else), letting you down to "just " your priests. And while your arty based doc has only arty more than basic brits, def doc has bunkers, pantherturms, huge infantry buffs and good tanks, and SE has 210mm nebels, flame nades, traps and tds that provide you some offensive variety in infantry or tanks as well.
-howitzers salvos are cheaper than any other in the game, allowing you to keep bombing pretty much non stop and you just have to hit the right target at the right moment.
-supercharge unlock increase even your heavy mortar and mortar pits range, providing you great passive defence against infantry and vehicles.
-your three artillery scouts have great abilities to coordinate arty and increase its accuracy, aimed salvos are amazing to immobilize and destroy even the biggest tanks.
- off-map barrages can help you vet your officers (which will improve significantly your infantry performances) and open a breach in enemy lines for your infantry or get rid of unexpected mgs/paks.
- priests have that good damage output that howitzers lack a bit, and they're very deadly even against vehicles, so you can try to use them to counter enemy arty vehicles.
-staghound is a great infantry and light vehicles hunter, has a great mobility and many mgs, and 75mm autocar is an early very effective arty unit which, with new HE system, i've seen killing almost entire infantry squads with a single shell, early fallshirms included.
-basic brits' units are overall quite decent, expecially achilles tank hunters and crusader tanks to stop infantry, well equipped tommies with LT too, so even without much variety you still have effective counters to everything.
Considered all theese aspects it's not a doctrine you can play on its own, but when you can coordinate properly with your mates it's literally an amazing support doctrine. I think the easiest playstyle would be setting up a decent defensive line, supported by mortars and use your artillery and scouts to counter every kind of indirect fire your enemy can use against your defences. Constantly ask your mates if they need a bombing somewhere is really foundamental, since you might give them a very quick and effective way to prepare their attack and saving them some resources which they can invest somewhere else.