Your experience is quite interesting and has me worried a bit, I'm still on map one I bought it and played little bit only, but then I had to get back to work.
I will let you know how my campaign is going when I get started on it.
May I suggest you buy Original War or Freedom Force those are both good RTS/RPGs and will cost you only 6 dollars.

Great. Some random guy finds a game too hard for him, and posts a REVIEW bashing it.
Go back to your Playstation.

Then would you mind pointing out what his error could have been, instead of just popping up and insulting him?

No. Bullshit "reviews" annoy me.

To be honest the guy admitted he hadn't even played it yet though made a review about it. Rather confusing to be honest.

There is always an easy mode of the game...
My advice, read what characters say during the game, you have to think to win, "one button gamers" wont find much fun here.
But if you pay careful attention to what happens, the game is rather easy on normal difficulty level and it is very rewarding to find, by yourself, the perfect tactic for certain scenario.
And writing a review based on one scenario in witch you have clearly not understand the game mechanics is rather lame...

There are very simple details that one can forget which leads to getting your butt kicked in the game. In the tutorial I was sent to fight against a tough guy with a hammer and I took about six or eight archers with me. As per the tutorial's instruction. I mean, it's just one guy against eight archers and myself, what are the odds? When I came back limping and bringing bad news to the archer's widows, I realized I hadn't even once tried out the healing waters on my inventory, which was probably the purpose of the whole thing. To figure out how to use stuff you have on your inventory.
So yes, you have to keep an eye on your objectives.

I'm playing on Normal, and I should be 5 or 6 missions into the adventure, and the difficulty seems quite manageable so far. Sure, you have to know when to retreat, and sometimes you need to leave your army behind while you flee to get more troops and get back to the fight - which some people might take some time to get used to - but it's not that difficult.

My biggest mistake was leaving my army lying in the open somewhere on map like in any other RTS, while I did other stuff. Turns out they get hungry and with hunger, they start to lose life. My druids were healing people left and right and they just wouldn't finish healing them up, until I realized standing around outside a stronghold got them hungry. Once I made a bunch of mules with food and sent them there, everyone got peachy green. Imagine how "well" they would fight on an empty stomach.
Another thing is the armies are so big and the fights so full of sprites I tend to lose my hero in the crowd.
I kinda find the jumpy run of the swordmen funny. It's like they go to battle hopping on the tip of their toes like freaking ballerinas.

The mission in question did not allow you to build any new structures, did not seem to provide any way of replenishing troops with food (preventing effective levelling of the troops), had no healing items available or druids available to heal.
The only way of completing it appeared to be to get new troops from the NPC in the main town, charge at the enemy using formations as best as possible, standing ground to hold the formation, and then getting slaughtered, running away, and repeating the whole process several times.
This was to get 1 of 3 objectives on the map, with the whole process being repeated again for the other 2 (with the potential of calling aid from another NPC, who promptly rode off so fast that by the time my troops caught up, the "help" had got slaughtered).
I'm not a complete beginner to either the RTS or RPG generes, being a bit of a Starcraft nut, and also rather a fan of the Dawn of War series, so I'm used to both large army and also small squad management games. And for the record, I don't own a Playstation, hardcore PC Gamer to the end; Cheers for the constructive reply.
This was all played on the Normal setting in the game, after going through the tutorial, the manual that came with the game, and the official forums to try and work out if I was doing anything glaringly wrong. I stand by my review and the 3 stars I gave the game. I also stand by the fact I un-installed it, as for me it was good, but just not balanced enough for decent play without becoming a bit of a fanatic and grinding the methodologies that the game demands you employ.
If all that seems like "[finding} a game too hard for [me], and post[ing] a REVIEW bashing it." as opposed to a playtest over 2-3 days, a carefully thought out response, and a heads up to people that might be interested in buying it, then I'll go find a 2nd hand playstation...or go back to Neverwinter Nights 2 for another playrun. Whatever. ;)