Hopefully I can offer a little insight…
I did Eng Lit, History & RS (many moons ago)
DC1 did Eng Lit, History, RS & Politics (dropped History after AS and continued other 3 to A2)
DC2 currently doing History, RS, Politics & Geog (likely to keep all 4 on next year to A2)
RS is an excellent A level - I know some will dismiss it as ‘less than’ other humanities but it really isn’t. It’s rigorous and very interesting. What board will your DC be under? We’re in NI so it’s CCEA for us and there are 8 different modules to choose from ranging from Biblical studies (Acts, Pauline epistles etc) to World religions (Islam) and Ethics, Philosophy or Church History so lots of scope for variety. As it happens my DC (at different schools) both have Ethics & Church History, whereas the school I used to work in teaches Acts & Islam. (Having done a Divinity degree myself and with current A level DC looking at Theology degrees I would highly recommend keeping RS in there if considering a BD/BTh)
English Lit is intense because of the coursework module in the second year. It’s a lot of work and if done correctly should be an independent study. A lot of schools ‘teach’ the coursework and spoonfeed their pupils through it (while doing their best to stick to the JCQ guidelines) but it really is meant to be an independent piece of work. My eldest loved doing it, and got a very high mark (72/75) but it was a huge amount of work with pretty much zero input or support from their teacher. The rest of the English content I think is fine - there’s less on the spec now than there was in the 90s when I did it. (no coursework component then though) There is a big step up at A level in all subjects but I do think RS and English are two which surprise a lot of people. In English it really becomes much more analytical at A level - much moreso than at GCSE - there is a lot less to do with characters or story arcs for instance, and much more about the techniques used by the author/poet.
History is A LOT of content. I’d say it was the most content heavy of my eldest’s subjects by far. 2nd one would say that Geog is also very content heavy, but history still is worse. From experience, a lot of pupils here in NI who start with 4 subjects (very normal in grammar schools here) and have history as one of them, drop it after AS due to the sheer volume of content. I know quite a few who have been put off history as a result of A level study. Having said that, I loved it when I did it. My eldest dropped it after AS, but current one is thinking of keeping all 4 on next year to A2.
3 essay subjects is fine - IF essays are your thing. For my two it’s natural so it was never a slog for them, but the hardest thing to navigate is that they are all looking for different things, and recommended structures and techniques are really quite different in the subjects your DC is looking at. An English poetry essay is a very different thing to a History source based question, which is very different again to an RS synoptic essay etc so while they are all essay based subjects, and yes, they will spend their life writing practice essays, there is a fair variety in the style, structure, technique and obviously content, to keep it interesting