I've found that a decked paladin (better than divine saves) resists energy drain easily, and basically is only vulnerable to con-targeting spells like plague (if elf rather than dwarf). And if you're decked, two rounds of combat and a strike of faith is much more painful than a shaman can easily afford. Let's say vs unprepped enemy your melee hits are MANGLES and strike hits are DEVAS. 100 hp, 150 hp respectively. Suppose each round of combat averages 1.5 hits on the enemy and strikes average 2 hits: that's 600 hp damage to unprepped. Against a shaman with protection and sanc, it's 225 damage.

The scenario is that you flee, haven, and they open with dispel or energy drain (and you save against drain). If they open with damage, you can strike or templars defense lag them for ~3 rounds of melee on them. It gets better if your mace stuns on third strike and your gear progs for more damage (or belt lag).

Basically your threat level rises disproportionately with gear, theirs only makes more hp for you to chew through, barring exceptional Hell gear or something. A string of unlucky hits and progs on them can kill them if they over-extend (e.g. by trying to dispel-initiate on you when they're at 60% hp), but a strong player won't die to a lone shaman if they're careful.

If you have faith of course you tend to win. But it's not as much of a shaman killer as it looks: divine intervention has two rounds lag, they just flee and re-sanc. Dispel is one round lag for them.

If they're Venom path and you're elf it gets nasty, I wouldn't take that fight lightly. But dispel on its own isn't all that scary to a geared paladin.