I notice that the xp requirement for morphed skill seems really high. For example, I took skill A at level 1, by level 8, I morphed it into skill A (morphed). Then I took skill B at level 12, and within the same level, it was level to skill B IV. However, when I look back at my skill A (morphed) it seems to has less than 1/4 xp needed to level to skill A (morphed) II. Skill A was in my hotbar all the time since level 1 while skill B was just added to my hotbar at level 12.

Do anyone experienced the same thing as me?

I disagree. Keep in mind, you can get to level 50 in this game... it doesn't stop at 20.

You're confusing level experience with skill experience. Skills are leveled by how often you use skills. Granted, you can gain "some" points just for having them slotted... but unless you actually "use" them, they advance slowly.

What the OP is saying, is that skills level very very quickly for the first 4 levels. At that point, you can morph them... but once morphed, he believes the skills then level too slowly.

I think this is short sighted. By level 20, you'll have roughly 5-6 skills morphed, and one or two skills at level 2 post morph. Keep in mind, you have a loooong way to go before you're max level. If your skills maxed out at level 20 or 25... you wouldn't be growing at all for 25 more levels. Your skills damage raises with each rank they go up. You'll need to pick skills that are important to you and level them up... that's part of the process. If you want to level tons of skills to their max potential... well, that's the "grind".

It wouldn't give you anything to strive for if all of your skills maxed quickly, and it would make everyone exactly the same at 50.

As I am only got invited to the beta weekend and level 13 currently, maybe I worried too much but I still feel and hope that the experience requirement for skill after morphed get tone down. That way, we will have more completed skills which you can play around with. Once thing about ESO which I like is options and choices. So many different skills for you to pick and combine into a build. Maybe the developers intention is for a morphed skill is to be the cake and additional levels are just the icings. Maybe we will be stuck with 2 sets of complete morphed skills at 5x levels, maybe we won't. However, I always prefer more different skill choices, more options.

I am curious what's the PTS testers feel about this and maybe they can enlighten us.

I don't see why this would be a problem...gives you something to work for later on.
There's SO much of the game...i got my tier 1&2 skills to morphed level 2..maybe 3..maybe even maxed i dont remember haha
I'm glad you don't just max level from level 1-20 and then get no more advancement from then on.