...Bother making a Hayato for the Link Skill?

Its hard to really show you what I mean, mainly because my chars are too high lvl to test it fully on, but it will be like this:

40k exp base exp
40k exp (this is your 2x exp card line)
100k exp (party play bonus exp 250%)
6k exp (mercedes link 15%)

Previously to these changes a 2x exp card would do this instead:
80k exp base exp
200k exp party play bonus
12k exp mercedes link

As you can see the exp is duplicated by 2x now, but later it will only add another 100% as if you were having 2 more members in party at a party play area, makes sense now right?

It made sense already.

Mercedes link is 15% not 30%.