I'd definitely wait until I had access to the Lihzahrd Temple, Chlorophyte, and Lihzahrd traps with which to build a nice arena before worrying about Expert Hardmode Eclipses. Not coincidentally, that's also when you'll get access to Solar Tablets and Solar Tablet Fragments.
Still haven't beat plantera yet, but I set up some heart statues & honey, and with Chloro gear & bullets, Holy Stormbow when Mothron showed up, the second eclipse went a lot better. Only got killed the few times she did the "sticking to you until you die" thing. Managed to get the sickle, shell, and Terra blade, woo!
And I guess that's the answer to OP's question, isn't it? No, it's not too hard, if you're not able to beat something, you're just not using every advantage. There are definitely a few mechanics that feel (are) cheap, but you can do it!